List of Ben 10 characters
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Main characters 
Ben Tennyson 
- Tara Strong - Ben 10 and Ben 10: Omniverse (4 years old in "Don't Drink The Water" and then 10 and 11 years old)
- Fred Tatasciore - Ben 10 (30 years old Ben in "Ben 10,000")
- Yuri Lowenthal - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse (15 and 16 year old)
- John DiMaggio - Ben 10: Ultimate Alien (36 years old in "Ben 10,000 Returns")
Benjamin "Ben" Kirby Tennyson, is the main protagonist of the series. He is a 10-years old (fifteen in Alien Force, sixteen in Ultimate Alien and Omniverse) child from Bellwood, who found the Omnitrix during his summer vacation with his grandfather Max and his cousin Gwen. The watch fastens on his wrist and gives him the incredible power and ability to transform into super-powered aliens, and then he uses his new powers and abilities to become a superhero, dealing with both earth and aliens threats, while trying to escape the alien warlord Vilgax, who pursue him relentlessly in order to retrieve the Omnitrix.
For most of time, Ben is portrayed as an immature, sometimes self-centered boy; in the beginning, he only helped people with the pleasure of being a hero. This leads Gwen, Max, and the others to doubt Ben and they wonder if he has what it takes to be a hero and he should keep the Omnitrix. He has matured dramatically and is a very capable good leader in the sequel Ben 10: Alien Force due to Grandpa Max's disappearance and the threat of the Highbreed Invasion, but tends to relax and (somewhat) turn back to his original self in the third season.
Despite his immaturity, Ben's actions are motivated above all by a strong and sincere will to help other people; he'll stop at nothing to protect his family or anyone in danger. Sometimes, his idealistic nature tends to make him act naive. Though often thought by many other characters to be quite unintelligent, Ben actually proves to be resourceful and cunning when needed, usually showing good adaptation skills when the Omnitrix doesn't provide him with the form he originally wanted. In the episode "Where the Magic Happens", Kevin shows surprise when Ben is able to memorize a sentence of magic symbols with a mere look. Gwen also states that he isn't working to his potential in school, to which he agrees. While attending the Plumber Academy, Ben seemingly does not pay attention to his classes or the drill sergeant, yet still achieves a grade of 95 upon completion of the course. During the Academy, he was unable to handle the training as a human so he uses the Ultimatrix to get him through the training despite his drill sergeant telling him not to use it. How much of that is the previous training Ben received from his grandfather and his actions in the episode is unknown.
At some point between the two shows, Ben had removed the Omnitrix, spending some years without it, because he chose to give up from his superhero career to have a normal life, though he kept the inactivated Omnitrix as a souvenir, however, Ben found out that his Grandpa Max had mysteriously disappeared while investigating what Magister Labrid calls "an alien conspiracy with Earth in the middle" leaving only an enigmatic holographic message for Ben. Despite Gwen's doubts, Ben decided to use the Omnitrix again in order to find Max. When he toned down his immaturity in the first seasons of Ben 10: Alien Force, he proved to be a capable leader for his team, although after his success at saving the universe from the Highbreed Invasion, his overconfidence caused him to revert to his immature personality as well as a very competent fighter, and also Ben, Gwen an Kevin became "Deputized Plumbers". However, after his successful attempt at ending the Highbreed Conspiracy on Earth, Ben grew famous and was celebrated as a hero throughout the whole galaxy, now known as Ben 10, and received awards from various Alien Ambassadors; this caused him to eventually relax and return to his immature attitude from the original series, with the addition of being somewhat cocky, much to Gwen's and Kevin's chagrin. To make it worse, Ben loses Azmuth's trust after a failed attempt to hack the Omnitrix. He became slightly more mature after defeating Vilgax.
Ben also discovered that he, his cousins Gwen and Ken, father Carl and Uncle Frank, have alien heritage, from a species called Anodite, though he doesn't have his grandmother's spark like Gwen. Although, in "Fame", it is shown that at the end of Ben's mission, his eyes turn pink noting that there might be a connection between him and his Anodite background. This is proven in "Ben 10,000 Returns" when he is able to conjure up an energy shield made of manna to block Eon's aging energy ray (though Gwen's powers are much more powerful).
In the two-part series finale of Ben 10: Alien Force, Ben lost the Omnitrix for Vilgax and was later forced to sacrifice it by ordering it to self-destruct. He then successfully took the Ultimatrix, a revamped version of the Omnitrix, from his evil twin Albedo. In addition to the original Omnitrix's shape shifting powers, the Ultimatrix gives Ben the power to turn into more powerful forms of his aliens, called "Ultimate's."
In Ben 10: Ultimate Alien, Ben's secret identity is revealed to the world and he's now a megastar superhero loved all over by kids. This series features Ben's new car that Kevin gave him for his 16th birthday in "Ben 10: Alien Swarm". Kevin says that he'll keep it (since Ben destroyed his own with Humongousaur), but Ben threatens to throw the new one if he can't keep it. Ben is seen frequently driving his new car, titled the "DX Mark 10" (shown as a Mazda RX-8 in "Alien Swarm") in Ben 10: Ultimate Alien.
Gwen Tennyson 
- Meagan Smith - Ben 10 (10 years old)
- Ashley Johnson - Ben 10: Alien Force, Ben 10: Ultimate Alien (15 and 16 years old), and Ben 10: Omniverse (11 and 16 years old)
- Tara Strong - Ben 10 (30 and 42 year old in "Ben 10,000" and "Ken 10")
- Haley Ramm - Ben 10: Race Against Time
- Galadriel Stineman - Ben 10: Alien Swarm
Gwendolyn Catherine "Gwen" Tennyson is Ben's ten-year old cousin (fifteen in Ben 10:Alien Force, and sixteen in Ben 10: Ultimate Alien and Ben 10: Omniverse).
In the original series, Gwen shares a love-hate family relationship with Ben. Before discovering her dormant magical and Anodite powers, she would help Ben by simply using her innate cleverness and intelligence. She is known to be a capable gymnast and martial artist and has received a black belt in taekwondo. Gwen is a very good student, especially in the episode "It's Not Easy Being Gwen", which shows that Gwen takes her education very seriously and in Ben 10: Omniverse, she is shown leaving for college.
Overall, her most notable skill is her incredibly strong magical powers and abilities. Having within her what Charmcaster calls a magical aura (which is bright blue in the original series, but changes to bright shades of pink, magenta, fuchsia and varying shades of violet in the two sequels), Gwen is capable of using various magical artifacts, charms, talismans, spellbooks and spells. On two occasions, Gwen has used the five Charms of Bezel to become a superheroine by the name of Lucky Girl. At first, her power and ability drew from the luck-granting Charm of Bezel, which innately gave her perfect luck. While wearing the charm, any action she took would result in a chain reaction benefiting her original intent, but usually injuring Ben in the process. She later brought back her superheroine identity after obtaining the Keystone of Bezel, which greatly increased and strengthened her natural abilities to superhuman levels rather than just affecting her luck. She was later forced to retire when the Charms of Bezel were destroyed. However, in a twenty-year alternate future timeline, thirty-year-old Gwen goes to the mystical dimensional realm of Bezel to receive a new set of mystical charms.
Five years later, in Ben 10: Alien Force, her magical powers and abilities have greatly strengthened and she is easily able to control and manipulate pink/magenta/fuchsia glowing energy from her magical aura to create energy blasts, shields, barriers, ropes, chains, stepping stones, and other weapons and items. Her paternal grandmother, Verdona, is an immensely powerful Anodite alien from the planet Anodyne, a free-spirited alien species who possess the power to manipulate and control a supernatural force-like substance called "manna," which is the very essence of all magic and life itself. Gwen is also able to take on an Anodite energy form just like her grandmother.
Kevin Levin 
- Michael Reisz - Ben 10 (Season 1, with 11 years old)
- Charlie Schlatter - Ben 10 (Season 2 and 4, with 11 and 43 years old in "Ken 10")
- Greg Cipes - Ben 10: Alien Force, Ben 10: Ultimate Alien & Ben 10: Omniverse (16 and 17 years old)
- Nathan Keyes - Ben 10: Alien Swarm
Kevin Ethan "Kev" Levin is an eleven-year old (sixteen in Ben 10: Alien Force, seventeen in Ben 10: Ultimate Alien-present) Human/Osmosian hybrid with the unique ability to absorb any type of matter or energy in order to utilize it in various ways.
Kevin was one of the antagonists during the original show due to absorbing various energies, an action that warps an Osmosian's mind. After accidentally absorbing energy, Kevin demolished his family's house, thinking that his stepfather, Harvey Hackett, had convinced his mother to throw him out. Running away from home, he eventually ended up in New York City and made a home for himself in the subway tunnels. Later he befriends Ben in order to absorb power from the Omnitrix's and seek revenge on everyone who treated him like a monster because of his abilities. However, a side effect was that although Kevin could change at will between the different aliens that were recorded in the Omnitrix (a skill that Ben lacked), Kevin could only look human for a short period of time. This prompted Kevin to blame Ben for his condition and go on a rampage, using the different aliens and their respective abilities to impersonate Ben. Eventually, Ben confronts Kevin in a battle which causes Kevin to turn into a chimeric hybrid of the alien forms. Though his hybrid form allows Kevin to utilize all of the abilities of Ben's different aliens, the power of the individual aliens is reduced. Eventually, Kevin ends up in the Null Void where he manages to regain his normal form and master his abilities under the guidance of a fellow inmate before escaping and becoming involved with the intergalactic black market. Despite lacking a proper formal education, Kevin possesses a vast scientific and technological knowledge of alien life and paraphernalia. For example, he even learned Astrophysics while on the streets. However, his help during the Highbreed invasion of Earth causes him to team up with Ben and Gwen, leading him to live his dream of being a Plumber like his father. He also reconciles with Ben and, over time, starts a romantic relationship with Gwen. Kevin has a car, based off a 1970's Dodge Challenger which is armed with Plumber and other alien technology.
Though he turned over a new leaf, Kevin still at times acts out of his own interests at time and has trouble forgiving others. During Vilgax's challenge to Ben, Kevin accidentally mutated into a living colossus composed of steel, Tadenite, concrete, and wood. As a result, Kevin had to wear an I.D. mask, an alien technology used by DNAliens to disguise themselves as humans, which Kevin used in public to appear human. During this second mutation, he learns the ability to turn his limbs into makeshift weapons at will. When the Omnitrix was destroyed, Kevin reverted to normal, but retained his ability to shape shift.
During the events of Ben 10: Ultimate Alien, Kevin absorbs the Ultimatrix's energy in order to stop Aggregor, sacrificing his mental stability in the process, and becomes insane and a monstrous combination of Ben's aliens once again. Kevin again goes on a revenge spree against anyone who wronged him. However, unlike when he was eleven, Kevin is more of an anti-hero rather than a true villain, and has shown that he still retains some of his heart and humanity despite his condition. This is best seen in "The Enemy of my Enemy", when he spared Gwen's life instead of killing her, saying: The only reason you're alive is because of what you used to mean to me. In the two-part episode "Absolute Power", Kevin absorbs the powers of Alan Albright, Manny, Helen, Pierce, and Doctor Viktor. In a last stand in Los Soledad, Ben as Ultimate Echo Echo, finally defeats Kevin and drains his powers, thus reversing his mutation and restoring his sanity.
Rook Blonko 
- Bumper Robinson - Ben 10: Omniverse
Rook Blonko is a Revonnahgander from the farm planet Revonnah. He is a new Plumber, assigned to Ben by Max after Gwen and Kevin left.
He is a top Plumber Academy graduate, being a highly skilled fighter. He possesses many Plumbers' weapons and technology, such as the "Proto-Tech Armor" and "Proto-tool", a shape-shifting weapon that turns into a sword, bow, grappling hook, blaster, etc.
Rook is an extremely skilled fighter with advanced knowledge and training. But he is a By-The-Book cop with no actual experience, always treating Ben as a superior rather than a friend or a partner. It is said that the reason he and Ben are good partners for each other is that Rook is all training, no experience, while Ben is all experience, no training. Rook has limited Earth cultural knowledge and an inability to understand sarcasm, in contrast with Ben's wise-cracking, taught by experience personality. As a result, Ben was initially reluctant to accept the collaboration, even feeling it was forced by Max, but starts warming up to him eventually. Rook, on his side, is well-aware of Ben's status as a hero and admires him for it. He does not use contractions.
Max Tennyson 
- Paul Eiding - Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse (60, 65 and 66 years old)
- Adam Wylie - Ben 10 (10 years old in "Don't Drink the Water")
- Jason Marsden - Ben 10: Ultimate Alien (17 years old in "Moonstruck" flashback)
Maxwell "Max" Tennyson is the sixty-year old (sixty-five in Ben 10: Alien Force, sixty-six in Ben 10: Ultimate Alien and in Ben 10: Omniverse) paternal grandfather of Ben and Gwen. Despite his age, Max has shown on multiple occasions to be highly athletic and a formidable fighter. He takes his grandson gaining superpowers and super-abilities in stride and supports Ben in any way he can. Max was once in the United States Army, had been in an astronaut program, and was a Plumber and has been through his share of scrapes; Ben and Gwen didn't know of this at first, believing him to have been a literal plumber. They began questioning this after several incidents in which he displayed knowledge and skills that a plumber would not normally have; everything from military-style hand signals to a working knowledge of nuclear reactors. Throughout the first season, it seems that Max knows far more about aliens than he lets on, which climaxes in the season finale, where it is revealed that he and Vilgax are old enemies, with Vilgax even going so far as to call Max "a thorn in his side". Before Ben got the watch, Max tried to keep the plumbers and the aliens a secret from his family because he wanted to protect them and he didn't want this life for his family; however, his plan failed miserably and he needed to learn to accept Ben and Gwen with this life. He begin to train them how to use their skills on the field. Keeping his secret from his sons had lead his sons to resent him and he never gave his sons a chance to learn about his life. He eventually learned the errors of his ways and he begins to realize that Ben and Gwen have what it takes to fight evil.
In reality, Max was indeed a plumber, but not the kind that Ben and Gwen thought he was. He was part of an organization called "The Plumbers", and Max is one of the leaders, known as a "Magister". It is unknown if Max's strange taste in food was acquired from his adventures to other planets during his career as a Plumber, or if its root can be found in his childhood. Max was to have been among the candidates eligible for the Apollo 11 mission, and would have gone were it not for other concerns.
Max is an old friend of an alien named Xylene. She, like all the other three-eyed aliens of her planet, has the powers and abilities of flight, telepathy, and telekinesis. She had intended to send the Omnitrix to Max, but Ben found it by accident during the camp trip. They seem to have been romantically involved and work well as a team. Xylene tries to convince Max to form a partnership and travel across the galaxy with her, but Max eventually turns her down twice: the first time due to his duties as a Plumber, and the second time due to his love for the kids.
He also had a romantic relationship with an Anodite alien named Verdona. They ended up having two sons, Carl (Ben's father), and Frank (Gwen and Ken's father). However it seems that their relationship had apparently ended as Verdona left Earth to return to her home planet, Anodyne. She was assumed dead by her husband in Ben 10: Race Against Time.
In Ben 10: Alien Force, Max plays a part in exposing the Highbreed conspiracy. He destroyed a Xenocyte hatchery by detonating a Null Void Projector, which- after removing its focusing lens- makes a "pretty good imitation of a hand grenade" and produces an explosion that covers over half a mile wide. Max appeared to have been killed in the blast, but was instead sent to the Null Void, where he, calling himself The Wrench fought against Doctor Animo who had taken over. Once the conflict is over, trains a new group of young Plumbers, at the same time informing Ben and the team of any alien threats.
Secondary characters 
The Plumbers 
The Plumbers are a special police force that operates in the universe. While there are some that work on Earth, there are others that work in different parts of the universe. Among the known Plumbers are:
Magister Labrid 
- Jeff Bennett – Ben 10: Alien Force and Ben 10: Ultimate Alien (flashback)
Magister Labrid is a plumber who appears in the two-part episode "Ben 10 Returns". He is an unspecified fish-like alien in a water-filled suit who was Grandpa Max's partner. He first appeared before Ben and Gwen when he thought that Ben stole the Omnitrix, he was taken down by Gwen when he tried to attack Ben, the three of them stakeout a weapons trade held by Kevin between the DNAliens and the Forever Knights, they managed to take down Kevin while the DNAliens and the Forever Knights got away. During the second fight with the Forever Knights, he was mortally wounded protecting Kevin which ended up damaging his suit enough to leak, Kevin states that he has some tape to repair it, but he denies Kevin's request, before he evaporates, he tells Ben, Gwen, and Kevin to complete their mission to stop the DNAliens. He also appears in a flashback in "Moonstruck" in which Grandpa Max recalls meeting Verdona for the first time and to help stop the Synthroid. In this episode, Max reveals that Magistar Labrid recruited him to the Plumbers.
Magister Prior Gilhil 
- J.K. Simmons - Ben 10: Alien Force and Ben 10: Ultimate Alien
Magister Prior Gilhil is a Plumber. He first appears when he encounters Ben, Gwen, and Kevin. Seeing as he hasn't considered the Highbreed a threat, he tells them to not get involved with the Plumbers. Darkstar later tips him off to a fight between Ben Tennyson and a Highbreed Lord, and he also ends up captured by Darkstar. After Gwen and the DNAliens defeat Darkstar, Magister Prior Gilhil made them honorary plumbers and then arrested Darkstar.
Magister Prior Gilhil reappeared in "Escape From Agreggor", where in a flashback; he ended up answering a distress signal coming from Aggregor's ship. When he finds the five captive aliens during an inspection, he ends up knocked out and killed by Aggregor who used his charged-up staff on him. This explained how Aggregor was in his outfit and his ship when he recaptured Galapagus.
Magister Patelliday 
- Rob Paulsen - Ben 10: Ultimate Alien & Ben 10: Omniverse
Magister Patelliday is a Pisccis Volanns Plumber (just like Magister Pike) who is the second-in-command of the Plumbers of Earth. He looks like the other Pisccis Volanns, but he wears glasses. He only appears in the end of "Mother of All Vreedles" to arrest Ma Vreedle.
He reappears in Ben 10: Omniverse. He makes cameos in "The More Things Change, Part 2" and "A Jolt from the Past" and he appears in "Gone Fishin", were he is kidnapped by pirates led by Captain Cork.
Blukic and Driba 
Blukic voiced by:
- Paul Eiding - Ben 10: Omniverse
Driba voiced by:
- Eric Bauza - Ben 10: Omniverse
Blukic (name is a pun on the director Butch Lukic) and Driba (name is a pun on the director Dan Riba) are Galvan Plumbers who work in the tech support sector.
They are not as smart as most of the Galvans, but are smarter than any human, and smart enough to repair the Omnitrix. Blukic and Driba they discuss very often, similar to Ben and Gwen when they were 10. Blukic is thin, while Driba is fat, which makes them a parody of Laurel and Hardy.
According to Derrick J. Wyatt, they are the galaxy's dumbest geniuses.
Plumber's Helpers 
This group is made of children of Plumbers, most are hybrids, part alien, part human, with super powers, most with powers of some aliens of the Omnitrix and the Ultimatrix. They are allies of Ben's team and are currently being training by Max after they worked in the war of the Highbreed; in the end, they become pupils under him. Much to Max's annoyance, they insist on calling the new team "Max Force".
In the season 3 premiere, Max and the other Helpers try to take down Vilgax in the park but they were stomped out of the way.
To test the Plumber's helpers, Max and Ben came up with a plan to trick Helen, Pierce, Manny, and Alan into believing that Ben had gone rogue, and attacked his Grandpa aboard a satellite. Each member of the Plumber's Helpers had initially decided to go on their own to stop Ben, but they were only able to defeat him when they worked together. Unfortunately, their battle with Ben had caused the satellite to fall towards Earth. To prevent the deaths of thousands, Helen, Pierce, Manny, and Alan decide unanimously to sacrifice their lives to cause the satellite to self-destruct. Max appeared in time to stop the self-destruct, stop the satellite from colliding with Earth, and tells the Plumber's Helpers that they had passed the test, and was on their way to Plumber's Academy. Cooper was absent in "Above and Beyond".
The Helpers returned in Ben 10: Ultimate Alien in "Absolute Power" Pt. 1, Alan mentioned all of them, except Cooper was defeated by Kevin who drained him of his powers, along with Dr. Viktor. What Kevin did to them after he stole there powers is unknown, but they may have gotten there powers back after Kevin was changed back to normal.
Cooper Daniels 
Cooper Daniels first appearance in the original series, he was given a ride home by Ben, Gwen and Max. Cooper is a genius with technology, in part thanks to his unique technopathic powers, which allow him able to mentally merge with and control electronic devices, both terrestrial and alien, either activating it or creating new machines and to communicate with any sort of machinery, which turned the color of his eyes into a bluish color with a robotic-like print on them to show his connection to technology; this power became crucial in defending the Mt. Rushmore base from the Negative 10. He was the first Plumber's descendant with special abilities introduced in the story, though it is not shown or explained if his powers come from being descended from an alien, or if they're just a special ability he has come to exhibit.
Cooper reappears as a teenager in Ben 10: Alien Force, where he's become considerably obese due to spending too much time in his lab on the computer. The DNAliens capture him in and force him to use his technopathic powers to build a mysterious arch and a holographic projector to hide it. He's released by Ben, Gwen and Kevin, and destroys the projector. Cooper has since developed a crush on Gwen, which she can't help but be annoyed about, although Kevin usually shows jealousy when other boys crush on Gwen, he's surprisingly good-humored towards Cooper's teenage feelings. In "War of The Worlds", after studying the Omnitrix's ability to restore the DNAliens to humans, he dismantles his suit to create ray guns that copy the effect.
In Ben 10: Ultimate Alien, Cooper has shown to have had a growth spurt and is now considerably taller and more muscular, his voice deeper, and his overall appearance like that of a surfer. While unknown to what degree, he was shown to have gained strength after his growth spurt, as he was strong enough to plow through a wood wall. In the episode "Absolute Power", he helps in creating a device that would cure Kevin of his amalgamated form. He reappears in "Prisoner #775 is Missing", where it's revealed he has become a Plumber.
Alan Albright 
- Zeno Robinson - Ben 10: Alien Force and Ben 10: Ultimate Alien
Alan Albright is a teenager half human, half Pyronite (Heatblast's species).
He wears his Plumber's Badge on his chest that was inherited his from his Pyronite father, which gives him a strong resemblance to Heatblast. Alan discovered his powers shortly before his first appearance, and he cannot control his powers very well, including the ability to fly.
Helen Wheels 
- Juliet Landau - Ben 10: Alien Force
Helen Wheels is half human, half Kineceleran (XLR8's species) and Pierce's adoptive sister.
She was originally part of a small team in the episode "Plumber's Helpers", young plumbers' apprentices, with Pierce and their friend Manny. Helen is smart, brave, kind and level-headed, though at times she usually tries to act rational and wise, making her mostly a mirror image of Gwen, usually prefers a more careful and less aggressive approach, causing occasional argument between her and Manny, sharing a love-hate relationship with him, and she might have a crush on him. Helen has quite skilled with computers and technology and has the same abilities as XLR8, as well as a visor, though it only covers her eyes.
Helen and Manny used to hunt all sorts of aliens they confused for criminals whom they would throw into an old Null Void projector, which they've mistaken for a disintegration weapon. Manny convinced Helen that Ben, Gwen and Kevin, were DNAliens, but the confusion is eventually cleared up after Ben proves that the Null Void projector wasn't a disintegration weapon. To rescue those they may have falsely imprisoned, because part of those they captured probably were Plumbers' kids, Helen and Manny travel into the Null Void. Later, Helen telepathically contacts Gwen for help against Dr. Animo, which Ben provides.
Manny Armstrong 
- Khary Payton – Ben 10: Alien Force
Manny Armstrong is half human, half Tetramand (Fourarms' species), though he seems to be slightly smaller and weaker, presumably because he's a hybrid.
Manny is like Kevin, hot-headed, aggressive, a rebel, and sometimes cocky, often willing to fight even when it may be not necessary. He shows an anti-hero personality and is stubbornly dedicated to their mission, immediately assuming that Ben, Gwen, and Kevin are DNAliens, he lacks his mirror's laid back attitude, often permanently angry and insulting to even his own allies, earning him the dislike of Kevin and Ben and forcing Helen to act as peacekeeper. Manny is finally convinced to listen after being brought down by Ben, after learning the error of their ways, Helen and Manny travel into the Null Void to search for those they've wrongly imprisoned.
He shares a love-hate relationship with Helen. When confronted with Helen's wiser personality as opposed to his hot-headed attitude, it causes them to fight often, though he is shown to truly care about her, as he was willing to attack Ben after he hurt her in "Above and Beyond". Several hints suggest Manny might have a crush on Helen in nearly all of their appearances.
Later in the Null Void, Manny is one of the resistance fighters battling Dr. Animo, a past battle cost him a hand, which has been replaced with a crude clamp. Much to Max's annoyance, he insists on calling the new team "Max Force", in addition to his Tetramand powers, Manny also carries plasma beams guns.
Pierce Wheels 
- Adam Wylie – Ben 10: Alien Force and Ben 10: Ultimate Alien
Pierce Wheels is half human, half alien, and the adoptive brother of Helen. His species remains unknown.
He has the ability to sprout quills from anywhere on his body, similar to Porcupine in "Ready to Rumble", and combines it with martial art skills. He first appears in a recorded journal having reportedly died in the "disintegration weapon" during a mission while working with Helen and Manny, but it is later revealed that he was actually sent to the Null Void, presumably through the projector they had been using to dispose of DNAliens and a number of other aliens. Like Manny is a mirror image of Kevin and Helen is the same to Gwen, Pierce is a mirror image of Ben on the team.
Ben is forced to spar with Pierce in order to see "The Wrench" (who actually is Grandpa Max) and loses, though Pierce later finds out that Ben let him win in order to be allowed to see the Wrench.
Pierce re-appears Ben 10: Ultimate Alien episode "The Purge", where he was on a date with a human girl, disguised with an ID mask. Two Forever Knights members catch him ordering him to leave Earth, but he refused and was killed. Matt Wayne confirmed his death.
Julie Yamamoto 
- Vyvan Pham – Ben 10: Alien Force and Ben 10: Ultimate Alien
Julie Yamamoto is a sixteen-year old Asian-American student (fifteen in Alien Force, sixteen in Ultimate Alien) and a tennis player, who is Ben's romantic love interest, sweetheart and girlfriend. Her first appearance was in the first episode of Ben 10 Alien Force, where Julie congratulates Ben on his soccer win, blossoming Ben's deep romantic feelings for her. Julie later in "Pier Pressure", plays a bigger role when Ben manages to ask her out on a date (with help from Gwen), their romantic evening at the pier was interfered by Ship, which Julie was kidnapped by accident, and Ben shows his secret when he was trying to rescue her, however, she liked the Omnitrix, which surprises him. Julie is quite accepting of Ben's Omnitrix-fueled exploits. Besides being good at tennis, she is also good in school.
Julie is very cheerful, but not always very comprehensible, because she is very worried, especially with her friends. And from "Duped", Julie became more skeptical of Ben when the fame slowly goes to his head, which causes friction in their relationship, causing a short break. However, in Ben 10: Ultimate Alien, Julie showed more interest in the relationship than Ben, she is similar to Gwen in Ben 10: Alien Force, that was very visible in "Hero Time", where she was no longer angry at Ben, but she was jealous of movie star Jennifer Nocturne because she kissed him after he saved her, later, Julie ends up kidnapped alongside Jennifer Nocturne by Captain Nemesis, then, after Ben saves her, he apologizes her by calling "his girl" and she forgave him for all his flaws, instead of Jennifer (she was saved by Gwen and Kevin at the moment). However in "Revenge of the Swarm", when she was kidnapped by Elena Validus because of Elena's jealous when she found about her, but when Ben finds Julie, frees her, and Elena used the Nanochips to stop him, Julie convinces her to stop, she seemed to have no jealousy or regret of Elena trying to keep her away from Ben until she convinced Elena to save his life; different from "Hero Time", but that she still cares for Ben, it's possible that she had known about Elena just recently when she was kidnapped by her, this was seen again in "The Perfect Girlfriend".
Julie returned in the episode 'Rules of Engagement' in Ben 10: Omniverse. She has been redesigned with longer hair worn in pigtails. It's also revealed that she and Ben are no longer a couple, after a misunderstanding on the phone. She now has a new French boyfriend, who is a photographer. Despite this, Julie and Ben promised to stay friends, after she saved him from Princess Looma.
- Robert David Hall – Ben 10
- Jeff Bennett – Ben 10: Alien Force and Ben 10: Ultimate Alien
- René Auberjonois - Ben 10: Omniverse
Azmuth is a thousand year old Galvan (Grey Matter's species), as well the genius who created the Omnitrix, part of the Ultimatrix, the "Unitrix", "Ascalon", and the first Galvanic Mechomorphs. Azmuth is an extremely intelligent being, even as far as Galvan go, Azmuth's scientific prowess and achievements have made him a respected scientist even to the other Galvans, Paradox has even called him the smartest being in the universe.
A thousand years ago, Azmuth was in a relationship with a female Galvan named Xenith, who attempted to stir him from harnessing the primal forces of the universe. Though he promised to view things her way, the planetary system they saw in perfect alignment inspired Azmuth to create Ascalon which can tap into the fundamental forces of the universe. Though he shrugged off the consequences of creating such a weapon, losing Xenith's love in the process, Azmuth is horrified to find that Ascalon was stolen by an Incursion who hoped to end the eons-long civil war between the many factions on his homeworld. The result however, was the destruction of the Incursion homeworld. Shocked by what he had done, Azmuth vowed to hide away the sword and gave it to Sir George, who used the weapon to defeat Dagon with the weapon sealed along with the entity's heart.
Soon after, Azmuth dedicated himself to peaceful sciences, one of which was the creation of the Omnitrix as an apology to both the galaxy and Xenith, to be a tool of peace in an act of repentance following the destruction wrought by his previous creation. It has a twofold purpose: it would promote inter-species understanding by allowing other beings to experience different ways of life, and it would also serve as a repository for the DNA of millions of species, preserving them in the event that any of them should ever become extinct. However, he was disgusted when some people, particularly Vilgax, considered it as a weapon. This causes Azmuth to go into hiding before being found by Ben who needed his help to deactivate the Omnitrix's self-destruct sequence, convincing him there is still hope for the universe as he enable Ben to access Way Big and returned to Galvan Prime. Since then, Azmuth became more optimistic as he attempted to make up for lost time such as attempting to aid Malware as shown during the events of "Trouble Helix".
In Ben 10: Alien Force, Azmuth's former assistant Albedo creates a copy of the Omnitrix. After the copy nearly destroyed a galaxy, Azmuth shows up and punishes Albedo by breaking his Omnitrix, leaving him de-powered and trapped in Ben's human form, before sending him to prison. He then stated that Ben is the only one who used the Omnitrix for good, and decides to let him find his own way to use it rather than advise him, saying that he has far more difficult challenges ahead and that he isn't the only one who believes Ben is the only one who thinks so. Later, Azmuth and Paradox warn Ben that the Highbreed are conquering planets and their fleet is heading towards Earth. And Galvan Prime was already conquered by then and its destruction would be the beginning of the end. Although he doesn't want Ben to fight, he realizes that there's no stopping him and activates the Master Control for the sake of the battle. When the Master Control was reset by the DNA wave Ben used to stop the Highbreed, Azmuth left to help rebuild Galvan without reactivating it. He shows a no-nonsense attitude towards the High-Breed's plan to eradicate Earth and he warmly tells Ben that there are more difficult battles to be fought in the future.
Following the defeat of Dagon, Azmuth removes the Ultimatrix and places a new Omnitrix on Ben. When asked by Ben if he is ready to learn the Master Code, Azmuth states that he'll consider this by Ben's 18th birthday. He deactivated the Ultimatrix after giving to Ben, and gave him a newly modified Omnitrix.
- Vyvan Pham - Ben 10: Alien Force and Ben 10: Ultimate Alien
Ship is a symbiotic of canine behavior produced by a Galvanic Mechomorph (Upgrade's species) named Baz-El.
He possesses the same powers as Upgrade, he can also alter his form to mimic any device he has come into contact with; even objects with substantially more mass, like the Forever Knights's space ship, after this, Ship became the transportation of Ben's Team until Ben 10: Ultimate Alien when Kevin got The Rust Bucket III. Ship's vocabulary is limited to the word "ship", the message its creator had sent it to deliver, the word is adopted as the creature's name, but it turns out that Julie seems to understand what he says to her, although in "The Eye of the Beholder", Ship speaks his first word other than "ship" which is "Julie", when he choose to be with Julie instead of Baz-El, which he wanted to sell him as a weapon.
Ship first introduced in "Pier Pressure", where since there, he became Julie's pet, after Baz-El gave him to her, Julie really cares about him, and so as Ship, having developed an attachment to Julie, also she treats him as a normal pet, not as a powerful weapon, as most of people see. Ship also can shape shift into different shapes.
- David McCallum - Ben 10: Alien Force, Ben 10: Ultimate Alien, and Ben 10: Omniverse
Professor Paradox is a time traveler who is biologically immortal and able to transverse time through sheer will. Paradox been described as a calm, free-going man; he talks much like a stereotypical scientist, with dialogue requiring higher knowledge to understand completely. He also has a habit of getting events that haven't happened yet (from the perspective of the viewer and those he's talking to) and those that have (from his perspective) mixed up, due to his travels through time. His calm personality also makes it difficult to tell when he's joking or not.
He was originally a scientist from 1952 who discovered special properties in quartz crystals and received government funding to work on breaking a hole in the Space-Time Continuum, code-named the Paradox Project, with his assistant Hugo at the military base Los Soledad during the Cold War. But a slight miscalculation caused Paradox to get sucked into the Event Horizon, where he remained displaced from time for a 100,000 years. Losing his mind and regaining his sanity, he gained a complete understanding of the Space-Time Continuum. Having long forgot his name, he renamed himself Paradox and uses his understanding to travel across time to make different parts of history better for others. At some point in his time-traveling career, Paradox separated the pieces of the Map of Infinity, which could lead a person to the Forge of Creation, and hid them across the universe, disguising them as objects which would be difficult to obtain, in order to prevent the map from falling into the wrong hands. Paradox also met Ben's future self in his adventures prior to meeting the future hero's younger self.
In his first appearance in Ben 10: Alien Force, Paradox soon learns that the accident that gave him his power also sent an extra-dimensional creature fifty years from the time of the experiment. Meeting Ben as they confront the creature, Paradox learns the monster is actually Hugo and manages to negate the monster's existence by keeping his friend from getting sucked it. After returning to Ben's present, Paradox was shocked that he didn't figure it out first as he gives an older Hugo to a behind-the-scenes look at eternity.
In the Ben 10: Ultimate Alien episode "Ultimate Aggregor", Paradox informed the team that Aggregor was using his old time travel equipment to achieve his goals. He also gave Kevin advice concerning the future, telling him that things would get worse before they got better, and to try to remember who his friends were. He also warned Ben "not to lean against the chronal randomization barrier", but doubted that he would listen. In "The Forge of Creation", Paradox appears to help the team to go to the Forge of Creation which is outside the universe, but is unable to stay with them as the Celestialsapiens there have "placed a restraining order on their home". Paradox later returns in "Ben 10,000 Returns", aiding Ben and his future self against Eon. Before taking his leave, Paradox leaves Ben with a cryptical warning concerning Sir George and Dagon.
Returning in the Ben 10: Omniverse series, wearing a steampunk attire, Paradox is revealed to have been fighting a time war as he is pursued by Eon for the Chrono Navigator he possesses. But with Ben's help, Paradox protects the timeline though the restoration erased their meeting during that time.
Jimmy Jones 
- Scott Menville - Ben 10: Ultimate Alien
James "Jimmy" Jones is a 10 year old kid who is a major fan of Ben, and it was he who found out Ben's secret and revealed it to everyone on the planet.
He runs a website with pictures of aliens around the world, including every alien Ben has ever turned into, even when he was ten. He watches Ben by alerting him about any alien activity he finds via the internet. In "Andreas' Fault", Jimmy is revealed to have a secret informant in the Forever Knights in the form of Foreverduke838 (whom Jimmy met online), Ben realizes that Jimmy is very useful for letting him do what he wants, even giving Ben "relationship advice" and helping on fights, as seen in "The Big Story", when Jimmy helped to save them, retrieve the Ultimatrix for Ben, and defeat the plant alien.
He wears a hoodie similar in design to Ben's jacket and has his old pants from the original series. Jimmy sent out a video that finally showed the world that Ben has the ability to turn into aliens, as he thought Ben would like the attention and money. He now helps Ben in some episodes, but gets cut short by his mother who wants him to take part in aerobics.
Aggregor's Prisoners 
These aliens are from the Andromeda Galaxy, and they were kidnapped from their planets by an Osmosian called Aggregor, he wanted to absorb the full powers and abilities of the five aliens he captured using a machine he had built back on his home planet and make himself invincible so he can obtain the "Ultimate Prize".
All them escaped from Aggregor's ship using a shuttle, and crashed a land on Earth on the coast of Florida, afterwards, Galapagus, P'andor, Andreas, and Ra'ad each split up to find a way off the planet while Bivalvan stays with the shuttle and attempts to repair it. But all the aliens were recaptured.
In "Ultimate Aggregor", after regain all them, Aggregor releases them, but takes control of their minds and has them attack Ben and his friends, to bring more time for his plan be successful. When Aggregor used the machine to drain the aliens' powers they faded away.
In "Absolute Power" Pt. 2, all the aliens that Aggregor killed and drained their powers were brought back to life after Ben and the others stopped Kevin, releasing their powers.
- Dee Bradley Baker - Ben 10: Ultimate Alien
Bivalvan (a play on bivalve, a term for clams and oysters) is a crustacean-like creature and Water Hazard's genetic donor.
Every night he would rise out of the ocean and raid NASA, steal equipment from their secret rocket project, and use them to repair the ship. Unfortunately if he had launched the ship, the nuclear bomb he used to ignite it would have destroyed most of Florida. Ben, Gwen, Kevin, and Julie were able to stop Bivalvan from launching his ship, scanned his DNA, and promised that they would send Plumbers to get him and send him back to his home planet. Instead, Aggregor arrived before the Plumbers and recaptured Bivalvan.
- John DiMaggio - Ben 10: Ultimate Alien
Galapagus (a play on the Galápagos Islands, which are home to the Galápagos tortoise) is a turtle-like creature and Terraspin's genetic donor. Like the other members of his species, he's gentle, kind, and easily scared.
One day, Aggregor attacked his home planet, captured him, and imprisoned him with the other four aliens he had captured. When the five attempt to escape Aggregor's ship, Galapagus suggests using his communicator to send out a distress message. Even though he and the other aliens are put back in the cell, his message is heard by Magister Prior Ghilhil, who boards Aggregor's ship and finds the five aliens, only to be attacked by him. Bivalvan, P'andor, Andreas, and Ra'ad escape again, but Galapagus seemingly betrays them to Aggregor in exchange for his own freedom. When Aggregor admits he wasn't going to free Galapagus, he admits he didn't intend to betray the others either and incapacitates Aggregor. He then leads the escape to a shuttle, which Aggregor shoots down and causes to crash on Earth. Afterwards, each split up to find a way off the planet while Bivalvan stays with the shuttle and attempts to repair it.
Seeking help, Galapagus attacked Bellwood's downtown to get the attention of Ben. While battling, Gwen notices that he hadn't actually harmed anyone, and convinces Kevin to use the translator in his Plumber's badge to translate his words into English. After hearing his story of how he escaped Aggregor, Ben scanned samples of his DNA for the Ultimatrix, and has him taken back to his home planet in a Plumber spaceship. However, Galapagus finds out the spaceship's pilot is Aggregor in Magister Prior Gilhil's Plumber suit.
Aggregor's needs for Galapagus's powers were made apparent in "Where the Magic Happens", as his species is immune to mana.
- Dee Bradley Baker - Ben 10: Ultimate Alien
P'andor (a play on Pandora's box, which if it was opened, it would release all the evil of the world) is a Prypiatosian-B trapped inside an armored suit that limits his powers. He's the most aggressive and hot-headed of the five aliens. P'andor is being more aggressive than others, and seemed to have a rivalry going with Bivalvan and had a tendency to berate Andreas for not thinking. Also is NRG's genetic donor.
Desperate to return to full strength, he ends up establishing a reward to whoever can break open the suit. When the hired help consisting of Buzz, Hammer, and Surgeon are unable to use the Taedenite to break it open, P'andor sends them to capture Kevin. Upon his hired help capturing Kevin, P'andor tricks him into releasing him from his containment suit (the only thing limiting his powers). Revealed as a living energy being, P'andor attempts to drain the radiation out of a nuclear power plant, but also his presence in the Earth without his suit was dangerous, because he is radioactive. Kevin and Ultimate Cannonbolt are able to trap him back in his suit and turn him over to the Plumbers who deport him back to his home planet. Unfortunately, their ship is intercepted by Aggregor who blasts the Plumbers out into space and recaptures P'andor. In "Too Hot to Handle", P'andor was the only antagonist between the Andromeda Galaxy aliens.
- Dee Bradley Baker – Ben 10: Ultimate Alien
Andreas (His name and the name of the episode "Andreas' Fault" are a play on the San Andreas Fault) is a large, bulky, yellow, armored alien with jackhammers and drills in his arms and is Armodrillo's genetic donor. He is reckless, as well as oblivious, proven when he repeatedly attempted to wreck a spaceship while still inside it. His intelligence is quite low and doesn't even know what an asteroid is. However, being dimwitted, he often uses these powers at the inconvenience of allies and enemies alike. His personality and actions are very similar to Rath. On the other hand, Andreas is a little more gullible than hardheaded as he tends to make attachments to pretty much anyone whom he thinks is nice or is the strongest (this was proven when he blindly followed P'andor who had over-powered Bivalvan and took charge). Andreas has shown him to be a gentle giant, getting easily scared and thinks most people are his friends.
Sometime after he separated from the others, he met up with Argit who became Andreas's "friend". Then he took command of the Forever Knights by threatening to use Andreas to destroy their castles. His plan backfires when the Forever Knights rebel and capture Andreas, Argit, Ben and his friends. Andreas is to be executed but Ben and his friends save him and he then consider them friends. When the Forever Knights set a weapon to self-destruct, Andreas decides to save his friends by absorbing the blast on Argit's suggestion. Andreas saved them and was assumed dead by everyone. Miraculously, Andreas survived but was greatly injured, which made it easy for Agreggor to arrive and capture him once more.
While he was on Aggregor's ship, he was much braver, but on Earth, Andreas's personality is like that of an innocent child. He scares easily but takes comfort in his friends, whether they are bad or good.
- Dee Bradley Baker – Ben 10: Ultimate Alien
Ra'ad (a play on Ra'ad the popular Arabic male given name for thunder) is an Amperi and the AmpFibian's genetic donor. Preferring to be quiet and observant questioning Galapagus's trust briefly and agreeing that Bivalvan's plan was the best. He also appeared somewhat controlling, having a short argument with P'andor over power but quickly changed his mind and went along with Bivalvan.
After learning that Aggregor had captured the others, Ra'ad attacked Ben, and blaming him, thinking he had given the others aliens to Aggregor. Ben defeated and captured him, but Ra'ad duped them to letting him go, under the pretense of friendship. Ra'ad then entered the Ultimatrix forcing Ben to change into his form, and slowly taking control of his mind, but while he was undercover, he kept the Ultimatrix off-line, so Aggregor couldn't track him. Kevin was able to force the Ultimatrix to reboot, knocking Ra'ad out of it. Sensing Aggregor's approach, he fled, leaving Ben and company to fight him. However, after being scolded about his cowardice by Kevin, he returned, saving Ben from Aggregor's attack. But in doing so, he ended up getting recaptured by Aggregor.
Sir George 
- Peter Renaday - Ben 10: Ultimate Alien
Sir George is the First Knight blessed with immortality at his birth, having founded the Forever Knights over a thousand years ago. For reasons unknown, George left the order and has been in hiding for centuries. He has a coin with the infinity symbol (∞), the same symbol as the seal that held the Lucubra.
George was born as Georgius in Ancient Rome in 231 AD. He acquired immortality at some point by unknown means, living for over 900 years, before becoming a knight in the medieval era. Sir George forged the seal that kept the Lucubra in the 4th century, and in 1131 he also defeated another inter-dimensional creature known as Diagon with the sword Ascalon, created and gave by Azmuth, because he said that George was worthy enough to wield its terrible power. George carved out Dagon's heart and pinning it to the ground with the sword, he sent it back to its dimension (probably by using magic as stated), becoming the basis for the legend of Saint George and the Dragon.
In the 1930s, he moved to the Bellwood Senior Village and lived there for over 70 years and where he first appeared in "The Creature From Beyond". He had a coin with the same symbol as the seal that held the Lucubra. He somehow knew when the seal was destroyed and left. At the end of the episode he was seen looking at the damaged seal, looking down, and then leaving. In "Prisoner Number 775 is Missing", Sir George arrives at Area 51, where he attacks the guards and removes the base, turning it into a new Forever Knights stronghold.
In "The Purge", Sir George appears during a meeting between Enoch, Driscoll, Patrick and Urian. After a brief fight with Driscoll, he is identified as the founder of the Forever Knights and unites the factions into one. Sir George's first order was the Forever Knights target the aliens living on Earth and remove them whatever way possible. He later sends Driscoll to lead the Forever Knight soldiers into attacking an alien air-lift area that Ben was guarding. Upon learning of Driscoll's defeat, Sir George is not disappointed as it was just a distraction for a bigger plan. Sir George has Driscoll lead the Forever Knights while he is away and to have the Forever Knights ready upon his return, "for the battle of 100 lifetimes". Sir George has been on a quest for several days since it to find Ascalon and Dagon's heart so that he might destroy the heart. Using a long series of calculations, Sir George found when and where the shrine that holds the sword and heart would appear next. Through the Flame Keepers' Circle and Vilgax hindered his quest, George reclaimed Ascalon and was restored to his youthful self as he prepares the Forever Knights for an epic confrontation against Dagon while promising to give Ben the sword should he fail to stop the menace.
In "Beginning of the End" and "The Ultimate Enemy", when the Flame Keepers' Circle make their move, George goes to Dagon's cave and he finds Vilgax breaking the seal before battling him after killing Conduit Edwards. But once Vilgax freed Dagon, George is killed by him and Ascalon goes to Ben's possession where he finished what he started. In the end, Ascalon returned to Azmuth alongside the Ultimatrix.
Other characters 
Cash and JT 
Cash is voiced by:
- Tyler Patrick Jones – Ben 10: Race Against Time
JT is voiced by:
- Adam Wylie – Ben 10
- Yuri Lowenthal – Ben 10: Alien Force (In "Ben 10 Returns" Pt. 1)
- Scott Menville – Ben 10: Alien Force (In "The Gauntlet") and Ben 10: Ultimate Alien
- Tyler Foden – Ben 10: Race Against Time
Cash Murray and JT are Ben's former bullies from school. Cash is taller and has darker skin, JT is the shorter and wears glasses; also JT and Ben were best friends in the first grade before Cash moved to Bellwood. They are modeled after series producers Sam Register and Tramm Wigzell.
In Ben 10: Alien Force, Cash and JT found an alien tech gauntlet in Kevin's car that shot lasers. While taking turns using the Gauntlet, Cash became addicted to the weapon's power, and attacked JT when he tried to take it from him. After beating Kevin and declaring himself the "coolest guy in the neighborhood" Cash challenged Ben to a one-on-one battle. With JT's support, Cash realized that the armor was controlling him, and broke free of its power. Since then Cash and JT have been more friendly towards Ben, and are among the first to show their support when Ben's identity as a "hero" is exposed to the public.
In the Ben 10: Ultimate Alien pilot episode "Fame" Cash and JT applaud Ben at school after his secret has been exposed. In "Reflected Glory", they try to take credit for Ben's plans, and use Oliver Thompson to help them to make a TV show in which they claim to be the brains behind Ben 10. Psyphon, on a mission to gain the "Power Decouplers" for the Forever Knights, goes after JT and Cash since they claim to be the brains behind Ben 10 and are therefore responsible for the defeat of Vilgax, Psyphon's master. In order to save themselves JT and Cash are forced to admit they were lying about everything causing Psyphon to turn his attention to Ben only. At the end, Ben was being killed by Psyphon, so they use the Power Decouplers to shoot Psyphon, taking him out and saving Ben's life, however, the shot breaks Oliver's camera, destroying everything they recorded, including the scene where they save Ben. With no footage and its stars discredited, Oliver subsequently cancels the show.
Tetrax Shard 
- Dave Fennoy – Ben 10, Ben 10: Alien Force, and Ben 10 Omniverse
Tetrax Shard is a Petrosapien (Diamondhead's species) mercenary, and the first alien species of the Omnitrix that Ben had met.
Tetrax was originally a selfish bounty hunter until he accepted the job to steal his people's sacred crystal and deliver it to Vilgax. After the galactic warlord used it to destroy his home world Petropia, Tetrax felt guilty, and became concerned about who he worked for, and started trying to be sure Vilgax would not get other weapons of mass destruction (such as the Omnitrix).
Under the alias of Hoverboard in his first appearance for his namesake flying device, Tetrax was hired by Vilgax with Kraab and Sixsix to take the Omnitrix from Ben. However, it's soon revealed he's actually working for another unnamed force that wants him to assure Vilgax doesn't get the Omnitrix. When he initially meets Ben, he criticizes his lack of strategy, and tries to take him with him in order to deliver the Omnitrix to his true hirer. When Kraab and Sixsix then choose to team up against Tetrax, Ben is able to use strategy to defeat the two of them, causing the Petrosapien to agree to let him stay on Earth, since the Omnitrix is in good hands.
Tetrax comes back in "Ben 10: Secret of the Omnitrix", where he helps Ben and Gwen travel in space to find Azmuth so he can disable the Omnitrix's self-destruct mode.
In Ben 10: Alien Force, Tetrax discovers the Petrosapien Crystal was actually a backup for his planet and his people, containing all their memory and DNA. Learning this, he stole it from Vilgax and freed Sugilite (Chromastone's genetic donor) from the Omnitrix, so he could use the crystal to bring back Petropia. Despite Vilgax almost killing Sugilite, the planet is brought back thanks to Ben.
In the Ben 10: Omiverse episode "Store 23," the Dimension 23's version Tetrax Shard assisted Azmuth and Sevenseven into reclaiming the Omnitrix from Ben 23. This reality's version of Tetrax Shard has a beard.
The Galactic Enforcers 
The Galactic Enforcers are a group of alien "super heroes" that Ben first encountered in their titular episode. Ben was part of the team only in that episode; he was only recruited because he had the Omnitrix. Ben resigned after realizing that he would be better without them.
In the episode "Ben 10,000", set 20 years into the future, Ben's otherwise perfect patrol route left them out of a job and they were forced to clean up after Ben, bringing the criminals he captured to the authorities. Near the end of the episode, Ben lets them deal with the Circus Freaks while he attends Grandpa Max's birthday party.
They appear briefly in the beginning of the third season episode "The Vengeance of Vilgax" Pt. 1. Vilgax was attacking their home-planet T-K, and challenged Ultimos to a duel but Tini and Synaptak apparently interfered with the duel causing Vilgax to attack the two and then defeat him. Vilgax then drained his powers with the help of Psyphon and then claimed their planet as part of his empire.
Ultimos is from the planet Specimen Prime and leader of the trio and he obeys the Galactic Code of Conduct a lot, without hesitation.
He has Superman-like powers, look and attitude and it is shown that he has a dangerous reaction to chocolate, effectively his "Kryptonite", Synaptak identified it as a common poison across the galaxy but Ultimos was still quickly able to recover. Upon arriving on Earth, with Ben's help, he and his team capture Sixsix and Vulkanus but the two escaped due to an argument between Ben and Ultimos on how to bring the villains in (Ultimos's by-the-book peaceful tactic compared to Ben's beat down tactic) but he still made Ben an honorary associate. Despite his by-the-book personality, he's shown to like Ben's approach to fighting, stating that it makes him feel free.
In "The Vengeance of Vilgax" Pt. 1, Ultimos has his powers drained by Vilgax and Psyphon after he was defeated. It wasn't mentioned what happened to him after that.
- Greg Ellis – Ben 10 and Ben 10: Alien Force
Synaptak is a floating telekinetic brain in a jar with a computerized face and tentacles and he is the second in command of the group.
Synaptak had the abilitiy to levitate and has psychic powers of telepathy; being able to read the thoughts of others, telekinesis; being able to lift opponents and objects up with the use of his mind, and can project mind blasts and force fields from his brain. Effectively the brain of the group, he's shown to have an enormous crush on fellow member Tini, showing great jealousy over Tini's crush on Ben, which Ben easily took advantage of, saving both his new teammates and his family from a rock slide. At the end of the episode, the two hook up.
In "The Vengeance of Vilgax" Pt. 1, Synaptak and Tini are defeated by Vilgax before his fight with Ultimos.
Tini is a female Tetramand (Fourarms' species) and easily the strongest of the team, complete with all of Fourarms's powers but with better control over them. Upon arriving on Earth, she immediately met Ben as Fourarms and developed a crush on him and throughout the episode, tried to encourage him to turn back into Fourarms much to Ben's dismay. She was not aware of Synaptak's crush on her until Ben manipulated him into using his telekinetic powers to hold back a land slide, and at the end of the episode the two started dating.
In "The Vengeance of Vilgax" Pt. 1, Synaptak and Tini are defeated by Vilgax before his fight with Ultimos.
Myaxx is a female Chimera Sui Genris (Vilgax's species) Azmuth's assistant, where she helped him in the creation of the Omnitrix, collecting several DNA samples for the Codon Stream, including the ones for Floraunas (Wildvine's species) and Ectonurite (Ghostfreak's species). However, since Azmuth didn't give her the credit she deserved, she left a genetic signature in the Omnitrix overwriting his, and walked away. Ironically, despite being a good fighter as well as the same species as one of the most dangerous warlords in the universe, she's quite a coward who doesn't like fighting and would rather try to walk away or escape if she has the chance.
In "Ben 10: Secret of the Omnitrix", Ben, Gwen and Tetrax finds her in the Prison Satellite Incarceron. Ben confuses her with Vilgax and attacks. After the confusion is cleared, Myaxx tells the group that she's the creator of the Omnitrix so they can get her out of prison, but is forced to tell them the truth once they escaped. She still agrees to show them where Azmuth is, as well as putting a device on the Omnitrix to reflect the Omnitrix's energy blasts back inside it (the energy blast only happen when the Omnitrix is in self-destruct mode). When Vilgax comes to Xenon (where Azmuth is), Myaxx helps Tetrax and Ben despite her cowardice, to fight Vilgax's minions. After Ben defeats Vilgax, Azmuth offers for her to be his assistant again. Though he admits he won't be able to treat her better than before, she agrees, preferring to be his assistant rather than go back to Incarceron.
Myaxx appears at the beginning of "The Final Battle: Part 1" warning Azmuth that Albedo stole the Ultimatrix. Her look is completely changed, giving her a more feminine appearance, red armor and pink eyes.
Carl and Sandra Tennyson 
Carl is portrayed/voiced by:
- Dee Bradley Baker – Ben 10
- Don McManus - Ben 10: Alien Force, Ben 10: Ultimate Alien, Ben 10: Race Against Time
Sandra is portrayed/voiced by:
- Tara Strong – Ben 10
- Beth Littleford - Ben 10: Alien Force (In "Grounded") and Ben 10: Ultimate Alien, Ben 10: Race Against Time
- Vyvan Pham – Ben 10: Alien Force (In "Ben 10 Returns Pt. 1")
Carl and Sandra Tennyson are Ben's parents and Gwen's uncle and aunt; Carl is Max and Verdona's son. In the live action film Ben 10: Race Against Time, Carl is depicted as a new-age style parent who wants Ben to have his "freedom," insisting on being called Carl, not dad, and letting Ben run off on mysterious adventures without asking questions. He seems to be even more laid back than his wife, and is seen at least twice telling her to let Ben have his fun. Sandra reveals that Ben is lactose intolerant.
They appear in the Ben 10: Alien Force episode "Grounded", when they grounded Ben after finding out that he has been using the Omnitrix without permission or informing him and his wife. Later, they help Ben defeat a Highbreed and allow him to keep his Omnitrix. However, they eventually realize that Ben is the only one who can save the world from the Highbreed, and allow him to continue.
In the Ben 10: Ultimate Alien episode "Hit Em Where They Live" where Carl is oblivious to the fact that Vulkanus, Charmcaster and Zombozo were a few feet away and about to attack him, and that Ben, Gwen and Kevin were battling them while he was putting a spare tire on his car. And Sandra was kidnapped by Zombozo, but is later rescued by Gwen as her Anodite form.
- Rob Paulsen - Ben 10: Alien Force and Ben 10: Ultimate Alien
Baz-El is a Galvanic Mechomorph whose name wasn't revealed until "Vreedle Vreedle".
He is a pilot who crashed and has spawned Ship to find someone who could help him; he wanted help from Ben because he thought he was a Plumber; and before he left, he allowed Ship to stay with Ben and Julie. In "Vreedle, Vreedle" where he hired the Vreedle Brothers to retrieve Ship for without knowing of their incompetence, he appeared in the court where he lost the trial on who kept Ship.
Baz-El returned in Ben 10: Ultimate Alien episode "Eye of the Beholder" where he was stealing crystals from the ruins of a planet inhabited by the Churls and been caught by the Stone Guardians. However he reveals that he has a job scanning the atmosphere of various planets and makes money on the side by stealing artifacts from the planets he scans which for purchase as part of his "retirement plan." This is how he earned the scorn of the Churls. When Ship felt him being in danger, and attempted to go and save him, Ben, Julie, Gwen and Kevin followed. After Baz-El was saved, Julie, believing Ship was better with him, attempted to give him back to him, but Baz-El insincerely stated he was going to sell Ship as a weapon causing the minute Mechomorph to choose to stay with Julie.
Verdona Tennyson 
- Barbara Bain - Ben 10: Alien Force (Elderly Human form)
- Juliet Landau - Ben 10: Alien Force and Ben 10: Ultimate Alien (Anodite form and teenager form in "Moonstruck" flashback)
Verdona Tennyson is Max Tennyson's wife, mother of Carl and Frank Tennyson, paternal grandmother of Ben and Gwen, and also could see that she is great-grandmother of Big Chill's proliferation. She is an Anodite alien from the distant planet Anodyne, who Gwen inherited the powers and abilities of control and manipulate mana, the substance of magic and life itself. Like all Anodites, Verdona is a free-spirited being. Though sometimes acting more mature and grown-up, she mostly acts like a playful child. There is also another side of Verdona which is somewhat amoral and uncaring, for example when she almost destroyed Ben and Kevin when they first confronted her, were it not for the intervention of Gwen and learning who they really were and when she was willing to destroy her granddaughter's physical human body to release the Anodite lying hidden deep within her.
They had meet in the beginning of the 1960s, probably in 1962, during President John F. Kennedy's presidency. Verdona left Anodyne in an unspecified time and was brought to Earth by a robot alien called Synthroid who had captured her and want to use her to power his world. They crashed and landed in St. Louis where she met and fell deeply in love with Max after he saved her; and then they courted each other and married, during this time she hid her Anodite heritage very well and blended in with society. During their time together, Verdona always had to deal with Max's occupation as a Plumber which she knew very well yet kept the knowledge from him, prompting Max to always lie to her every time he left and eventually after a long, happy and yet somewhat distant relationship, they parted.
They had two sons together, Carl and Frank. However neither of them showed any signs of inheriting her powers and abilities. When they were grown up and out of the house, she returned to Anodyne; after so many years on Earth, Verdona wanted to get back in touch with her background. She once came back to Earth to see if any of her grandchildren had inherited any Anodite abilities and powers from her, but saw that none did. Only several years later, she found out that Gwen, her granddaughter had developed powers and abilities of her own. It should be noted that Big Chill is in fact Ben, which makes Big Chill's offspring Verdona's great-grandchildren but it is unknown if they even could inherit her powers and abilities or if the energy from the Omnitrix will prevent them from having "the spark."
She apparently favors Gwen over Ben, due to the fact that he did not inherit any powers and abilities from her so she just put him aside, which was shown when she magically conjured tape on his mouth so that he could not speak, that was until after their final fight against each other did she see just how much Ben cares about Gwen, the two reconcile on good terms afterward. She also has an uncanny sense of humor that was passed on to Ben, although Ben inherited his grandmother Verdona's spirit, sense of humor, and overconfidence, he also inherited his grandfather's determination, adventurous and self-sacrificing attitude. Also, she was shown to be a strict disciplinarian and shown to be serious when she needs to be, when Sunny went way out of line.
In Ben 10: Race Against Time, Max told Ben that his paternal grandmother had passed away, although this might be a lie. As Ben was likely not ready for the truth about his grandmother being an alien yet as he was ten at the time.
She appears first time in "What Are Little Girls Made of?" when she explained everything to Gwen about her alien inherited, and offered Gwen to come back with her to Anodyne to reach the full potential of her powers and abilities (which would require seventy-five years), but Gwen had refused the offer. Verdona then shed her human body, revealing her true Anodite form, and thought that Gwen was too young to make her own decisions and decided to destroy her human body to free the dormant Anodite inside, but the two boys' stepped to defend Gwen. After a brief battle Gwen explained to her that she would rather stay on Earth with her friends and family, Verdona then tells Gwen that Max should have been an energy being like them, expressing her deep longing for him and that her desire to take Gwen with her could be just a front to fill the void in her heart. Verdona then claimed to return every so often to see how Gwen is doing.
Verdona returned in "Girl Trouble", where she was able to overpower Sunny (who was attacking Gwen) and she took Sunny and her boyfriend Antonio back to their home planets and allows their parents to deal with them.
Natalie Tennyson 
- Juliet Landau - Ben 10: Alien Force and Ben 10: Ultimate Alien
Natalie "Lili" Tennyson is Gwen's mother, Ben's aunt, and the wife of Frank Tennyson (Carl's brother). She looks like Gwen, with shorter hair. She appears first time in "What are Little Girls Made Of" when Verdona comes to Earth to visit Gwen and Frank. She has shown to be displeased with the heritage of Verdona.
Lili doesn't seem to be particularly too fond of the Tennyson family, as she is usually complaining about them by saying they're not as "formal" as her side of the family, possibly due to the fact that some of them are not completely human. She also said that Ben has bad table manners while castigated her father-in-law's fashion sense. She was also seen to have disagreements with her mother-in-law Verdona, making piericing stares at each other at every given opportunity. This animosity between the two is yet to be explained.
She appears later in the Ben 10: Ultimate Alien episode "Girl Trouble" where her niece Sunny stays with them for a while despite Gwen's objections. She later reappears in "It's Not Easy Being Gwen," where she has Gwen help out with writing and mailing out letters to her side of the family for a regal-like party. She shows in this episode that she is as fond of Ben and Grandpa Max as Verdona, noting that Max's food is inedible and Ben doesn't have the best table manners.
Reinrassic III 
- Richard McGonagle – Ben 10: Alien Force
Reinrassic III, also called Reiny is a Highbreed, the seventh son of the Noble Highbreed House of Derazza, direct descendant of the Pure Blooded High Order of Rarsect.
He was first introduced in "Alone Together", where Ben was forced to work with him while trapped on the desert planet Turrawuste, though they needed each other to survive (indeed saving each other on multiple occasions), Reiny showed the typical Highbreed hatred of who they wrongly call "lesser species", forcing Ben to walk ten paces behind him and insulting him constantly, even yelling at him for touching him while saving his life. Due to not being accustomed to human introductions, when Ben introduces himself as "Ben, Ben Tennyson", Reinrassic refers to him then on as "Ben Ben Tennyson". Reiny eventually lost his hand saving Ben from a Rodilla Dentia, and then he used Swampfire to reattach it back, much to the Highbreed's surprise. Eventually they made it to the teleporter, but due to him forming a friendship with Ben, he banishes himself to Turrawuste, believing himself tainted by him.
He returns playing a brief but important role in the final battle with the Highbreed in "War of the Worlds: Part 2", after Ben healed the genetic damage in all Highbreed by fusing them with alien DNA. Reinrassic was unaffected by this because of his healing from Swampfire, as the vine used to reattach his arm has now spread up to his elbow and changed his DNA as well. He, despite his original self-imposed exile, realized that the Highbreed's views on other species were wrong and that being fused with another alien's DNA wasn't a curse, but rather allowed them to survive. This caused the Highbreed Council to elect him as the new Highbreed Supreme, the leader of all Highbreed. He called off the invasion and show Ben respect.
In "If All Else Fails", Reinrassic III aided Ben to stop a Highbreed Failsafe weapon left over from the war, which had been activated by a Highbreed Officer who was unaware the war was over. He told the officer that he is now the Highbreed Supreme, showing the Imperial Seal. He ordered the officer to shut the weapon down, but the officer revealed once it was activated it cannot be stopped. However Ben and Gwen came up with a plan to enter the weapon and deactivate it from the inside. They managed to stop it. The Highbreed Officer took control of it, preventing it from destroying a Nuclear powerplant. Reinrassic congratulated Ben for stopping the weapon, but Ben revealed the Highbreed Officer's sacrifice. However, Reinrassic told Ben that the Highbreed who died was a soldier doing his duty and that there was no greater honor for a Highbreed.
Elena Validus 
- Alyssa Diaz - Ben 10: Alien Swarm
- Tia Texada - Ben 10: Ultimate Alien
Elena Validus is the daughter of ex-Plumber who appeared and had a large role in the live-action film, Ben 10: Alien Swarm. According to the movie, she hung out with Ben and Gwen. During this time she and Ben became close, he helped her join the school soccer team, speaking up for her when the other players wouldn't let her join and eventually became the team's MVP. She was Ben's first major crush, but she was forced to leave Bellwood after her father Victor Validus was caught stealing alien tech from the Plumbers (Max never told Ben or Gwen why Elena and her father moved away). She eventually discovers her father had been taken over by the Hive Queen and seeks help from Ben and the Plumbers. As Nanomech, he goes into her dad and he kills the Queen, who controlled the Nanochips. Elena's father was freed, but apparently died shortly after the events of the movie.
Elena returns in the Ben 10: Ultimate Alien episode "Revenge of the Swarm", where she is shown studying the remaining Nanochips. After meeting with Ben to discuss a strange series of events involving Nanochips, Elena begins to display a disturbing attraction to him, which eventually leads to her kidnapping Julie in an attempt to ruin her relationship with Ben. When Ben finds Julie bound and gagged inside one of Elena's locked rooms, Elena goes berserk and reveals that the Nanochips she had been studying had taken over her body. After nearly killing Ben, Elena eventually regains control of her body long enough to seemingly commit suicide by walking directly into a Nanochip-destroying force-shield that she had developed. Though Julie attempts to comfort Ben by telling him that the real Elena had likely died a long time ago, Ben tells her that he thinks that a part of Elena must have survived long enough to save his life. However, some nanochips start to reactivate themselves after Ben left. Later in "The Perfect Girlfriend", Elena was revealed to be alive despite her sacrifice but returns to her villainous ways when she disguises herself as Julie. In her Julie form, Elena tried to do everything possible to make Ben happy. She also injured Gwen's ankle by pushing her down an elevator shaft and attacked Kevin with a duo of building-monsters while he was spying on her but Ben defeated it. Once Ben finds out that Julie is actually Elena, he fights her but loses after she chokes him with nanochips. Julie tells Elena that if she kills him, then no one can have him. At the end of the episode, Elena retreats "knowing what hate feels like" and promises to return.
Unlike other Plumber's Kids, Elena is completely human, and has no known special powers (at least in her first appearance). However, she is a capable fighter and exceptional martial arts (skilled in both armed and unarmed combat). According to Ben she is also great athlete, becoming their school Soccer team's "Most Valuable Player". A Galvan Plumber instructor also mentioned she was one of his best students, and might have become a great Plumber. While processed by the Queen, she displayed the ability to transform into a full size Nanomech/Human Hybrid, with the powers to control the Chips and shape them into whatever shape she pleased.
Victor Validus 
- Herbert Siguenza - Ben 10: Alien Swarm
- Brian George - Ben 10: Ultimate Alien
Victor Emilio Validus is the father of Elena and an ex-Plumber. He is the former pupil of Max, who planned on passing command of the Plumbers to Validus and retires. However, he was discovered stealing alien technology (a serious violation of Plumber regulations). Feeling deeply betrayed by Validus, Max did not believe him when he explained that the alien technology he stole was in reality an alien species known as the Hive.
Prior to the movie Validus was studying the chips to find a weakness. During his studies he became host to the Queen of the hive, using his plumber knowledge the queen upgraded the chips and later used his body to mass-produce the chips
Victor reappears in "Revenge of the Swarm". He was presumed dead, his cause of death was unknown. His daughter, Elena, found some of the Nanochips and studied them. It turned out that she was being controlled by them, and could make them shape shift into anything.
Colonel Rozum 
- John DiMaggio - Ben 10: Ultimate Alien
Colonel Rozum is a United States Air Force officer with access to high profile information, even about the existence of the Plumbers, and has personally known Max Tennyson.
He first met Ben and the team in "Fame", where he was stationed at a base in Florida overseeing the construction, and later investigating the theft of the high powered rocket engines being developed by NASA to advance Earth to interstellar travel, using an experimental engines that used a form of controlled nuclear explosion as a means of propulsion. They were targeted by Bivalvan.
He returns in "Ultimate Aggregor", Rozum is given the case and is aware of what the government considers to be a failed time travel experiment, the Paradox Project, using an Entropy Pump to generate a weakness in the fabric of space-time allowing travel through time. Rozum was frustrated that Ben's team already knew about the project, due to it taking him years of hard work to gain the clearance necessary. He wanted their help to stop Aggregor from using the Entropy Pump, giving his military strength to assist them should they need. It is in this encounter that he reunites with Max Tennyson (which may have been from Max's days as an astronaut given Rozum's connections to NASA) and meets Professor Paradox for the first time, where he initially refers to Rozum as Major.
He also appeared again "Prisoner Number 775 is Missing" when area 51 was attacked. Max was outraged to find out that Area 51 was a prison for any aliens that had been caught by Rozum and the military, without due process. One of the Prisoners escaped, and attempted to get revenge on Rozum for his unjustified decades of imprisonment that cost him the life of his family by targeting Rozum's family. After Prisoner 775 was defeated by Ben and taken in by the Plumbers, Rozum showed no remorse over the situation of the prisoner, declaring that he was serving his country and planet, severely putting a strain on his relationship with Max and the team.
- Molly Quinn – Ben 10: Ultimate Alien
Unitrix (Uni means one, in contrast of Omni meaning all) also known as Eunice is a prototype of the Omnitrix created by Azmuth which can absorb, contain and recall the DNA of different species.
Eunice was first introduced in "The Transmogrification of Eunice", when Azmuth lost her, and he hired Sunder to find her. When Ben, Gwen and Kevin find an alien pod, Gwen opened it where she ended up cut by the pod door and the Unitrix became a blonde-haired girl who was unaware of her past. After Gwen gave Eunice some of her extra clothes, Ben got a crush on Eunice and so as she. During the scuffle with Sunder in a muddy area, Azmuth arrived and cleared things up. He stated that Eunice was actually a Unitrix, a prototype of the Omnitrix created when he wanted to preserve alien DNA. Following a brief argument, Ben allowed Azmuth to take on Eunice as one of his assistants on Galvan Prime as a compromise. Azmuth also states that when Gwen cut her hand trying to open the pod containing the Unitrix, her human DNA was sampled and then randomised it (which explains why she has blond hair) creating Eunice's human form.
In her true form, she is a cylinder core, similar to the Omnitrix and Ultimatrix, however, the core resembles a container instead of a watch, but does feature a control dial that, when pressed down, turns it to its mobile DNA form (in this case, Eunice). As a prototype Omnitrix, the Unitrix is capable of storing DNA of different species, unlike the Omnitrix and Ultimatrix, she is not connected to the Codon Stream or Primus, limiting it to a single DNA sample. Eunice was also shown to be able to absorb DNA and powers of several animals and then to manifest traits of these animals without changing form, the powers and abilities she absorbs from aliens and animals last for about ten minutes. She managed to copy the hopping abilities of a rabbit, the strength of a bear, and the flexibility of a snake. There is also a green rectangle on the back of her neck and when Sunder pressed it, it turned her back to the Unitrix. In addition, local wildlife seemed to be attracted to her to the point where normally shy animals would gather around her and render more dangerous animals (like a bear or snake) docile towards her and others, this capability was likely included by Azmuth as a way for the Unitrix to easily obtain DNA samples from them, possibly to protect her and the item from danger since it's only temporary and the Unitrix can only contain one DNA sample. She also received an upgrade to have a one way link subspace link to Primus for uploading DNA samples. However, having the link active can cause parallel signal interference which could cause the Ultimatrix to lose its connection to Primus until it's shut off.
In "Simian Says," Eunice (now sporting a different outfit provided by Azmuth) goes to investigate the Arachnichimp's planet when she doesn't detect their DNA in Primus' Codon Stream. She helps Ben and company fight Mizaru and the Xenocyte-possessed Arachnichimps. When Eunice got infected by the Xenocyte, Ben was able to hit the button on her neck causing Eunice to regress back into the Unitrix.
- Patrick Cavanaugh – Ben 10: Ultimate Alien
Winston is a member of the Forever Knights and a squire to Sir Cyrus.
He was attacked by the Lucubra and turned into a mind-controlled slave. He was seemingly cured when Gwen the Lucubra back to its home dimension. However, like everyone attacked by the Lucubra, Winston becomes a thrall of Diagon and unconsciously becomes an Esoterica.
In "A Knight to Remember", Winston is a FKC member because he had been mind controlled by the Diagon. Under its control he informed the rest of the Flame Keepers' Circle of where to find Diagon's heart and Ascalon. When Vilgax gained the sword and the heart, Winston, still under the control of Diagon, tricked Vilgax into breaking open the Seal into Diagon's dimension and reuniting him with his heart.
He is killed by Conduit Edwards in "The Beginning of the End" when he saved Sir George. He had been declared a Forever Knight by George in death.
Mr. Baumann 
He first appeared in "The Purge" when Ben and his team wanted to ask about the Forever Knights at the time when the Forever Knights have been hunting aliens on Earth.
He reappears in the Ben 10: Omniverse episode "The More Things Change" Pt. 1. When Ben comes to the store to defend it against Bubble Helmet, Fistina, and Liam (who were working for Psyphon in his racketeer activity), Mr. Baumann begs him to leave, referring to past instances where Ben caused major damage to the store. When the alien trio fight with Ben and Rook, Baumann despairs over the damage.
In "Special Delivery," Ben's fight with Thunderpig ends up wrecking Mr. Baumann's car. Mr. Baumann has Ben perform deliveries to him without the involvement of the Omnitrix. When Ben manages to finish his deliveries, Mr. Baumann gets his car fixed. But when he was 16, Ben as Way Big threw one of Mr. Baumann's trucks into space to stop Dr. Animo's mutant mosquito. It falls from orbit (when Ben threw Sunder's glider into space and knocks the truck from orbit) and wrecks Mr. Baumann's house. Mr. Baumann gets angry, but Ben runs away as Mr. Baumann shouts "I know where you live." Mr. Baumann then sits in his recliner crying as it starts to rain.
In "The Frogs of War" Pt. 2, Mr. Baumann allows Gwen, Kevin, Blukic, and Argit to use one of the hidden rooms in his store to make a plan to stop the Incurseans.
- Tara Strong - Ben 10: Omniverse
Pakmar is a short alien and self-employed entrepreneur who first appears in Ben 10: Omniverse.
He first appeared in "The More Things Change" Pt. 1, when his Toilet Emporium had been destroyed as part of Psyphon's protection racket.
In "Of Predators and Prey" Pt. 1, Pakmar is shown to have started a pet shop in Undertown when Ben arrives looking for a dog whistle that matches the whistling that commands Khyber's Dog. Pakmar was still angry at Ben for being partially responsible for the destruction of his Toilet Emporium. The pet shop ends up destroyed during Ben's fight with Kyber's Dog.
Professor Blarney T. Hokestar 
- Charlie Adler - Ben 10: Omniverse
Professor Blarney T. Hokestar is an alien con artist, seeking profit yet he is not maliciously attempting any crime. Ben first meets him in "Have I Got a Deal For You" where he was working on a miracle elixer that is made from a small Screegit. When Pax tricks Ben into freeing the Screegit from its cage enough for it to be exposed to Earth's nitrogen and grow to giant size, Professor Hokestar helped Ben by telling him how to defeat the Screegit. After Pax and Solid Plugg were arrested by the Plumbers and the Screegit is in the custody of the Plumbers, Ben tells Professor Hokestar that if he ever comes near the Screegit, he will have him handcuffed to Pax for a year.
In "Store 23," Ben, Blukic, and Driba find Professor Hokestar operating the 23rd Mr. Smoothy restaurant which contains a dimensional transporter that Professor Hokestar was using to sell Mr. Smoothy drinks to different dimensions. One of these dimensions is Dimension 23 where Ben meets that reality's version of Ben. While Ben works with his Dimension 23 counterpart, Professor Hokestar helps Blukic and Driba work to get the dimensional transporter working. With help from Dimension 23's Azmuth, Professor Hokestar, Blukic, and Driba were able to perfect the dimensional transporter.
The Kraaho are a species of hot-blooded tungsten-based aliens that thrive on warm temperatures.
- Corey Burton - Ben 10: Omniverse
Seebik was the former leader of the Kraaho. He and the Kraaho first appeared in "Hot Stretch" where they planned to bring out Earth's magma so that they can survive. This plot was thwarted by Ben, Rook, and Ester. Seebik then handed the role of Kraaho leader to Ester.
In "Special Delivery," Seebik and a few other Kraaho loyal to him attempt to take the white Dwarf Star core from Ben. When Ben asked Seebik if Ester knew what they were doing, he replied "I hope not" implying that he was going rogue. He and the villains that assisted Psyphon were repelled by Ben.
- Tara Platt - Ben 10: Omniverse
Ester is a Half-Kraaho who first appeared in "Hot Stretch." She was seen stealing a fusion core from a building and was chased through Undertown by Ben and Rook all the way to where the Kraaho were living. She later helped Ben stop Seebik and the Kraaho from bringing the magma up from the Earth. Afterwards, Seebik made Ester the new leader of the Kraaho. According to Ester, the Kraaho will now live in peace with both Bellwood and Undertown. While getting some lemonade to cool off, the Kineceleran children pass by and calls Ben Ester's boyfriend, likewise Ben asks Rook if he had a shot with her, implying a possible relationship of Ben and Ester.
In "Rules of Engagement," Ester comes to Ben for help when the Kraaho are attacked. They find that the person attacking the Kraaho is Princess Looma. During Ben's fight with Princess Looma, Ester, Julie, and Herve are captured by Princess Looma to be involved in Princess Looma's wedding of Ben. After Princess Looma leaves and Julie agrees to remain friends with Ben as she leaves with Herb, Ben leaves with Ester to repair the Kraaho village.
Omnitrix and Ultimatrix aliens 
- "http://www.formspring.me/DerrickJWyatt/q/344344429580017005". Archived from the original on 2013-02-21.