Clayface
Clayface is the identity used by a number of shapeshifting supervillains who have battled the Batman. He is notable for being a classic villain who is metahuman rather than a deranged 'normal' human being like most in the Batman's rogues gallery.
Basil Karlo (aka Ultimate Clayface)
The original Clayface, Basil Karlo, appeared in Detective Comics #40. He was an actor who was driven mad when he heard of a remake of the classic horror film he had starred in. Donning the mask of the film's villain, the Clayface, he embarked on a murder spree among the cast and crew of the remake. He was foiled by Batman and Robin, and incarcerated in Arkham Asylum.
Much later, during the final stages of the Mud Pack Event (see below), he was imbued with abilities similar to those of Clayfaces III and IV, and was dubbed the "Ultimate Clayface".
During the "No Man's Land" event, Basil Karlo battled and was defeated by Poison Ivy in Robinson Park. It appears the Ultimate Clayface was destroyed in this battle, but has resurfaced as a member of the Secret Society of Super Villains.
The name Basil Karlo, and his career as a horror film star, suggest a reference to Boris Karloff.
Matt Hagen
The second Clayface, Matt Hagen, first appeared in Detective Comics #298. A treasure hunter, Hagen found a mysterious radioactive pool of protoplasm in a cave. Immersing himself in it, he was transformed into a malleable clay-like form which could be shaped into almost anything he desired, though this was only a temporary effect, requiring him to return to the pool periodically in order to maintain use of his powers. Hagen was ultimately killed during the 12-issue limited series Crisis on Infinite Earths. During the Mud Pack storyline, the other villains that used the name Clayface gathered Clayface II's remains and made him a post-mortem member of the Mud Pack.
Preston Payne
The third Clayface, Preston Payne, first appeared in Detective Comics #478. Suffering from hyperpituitarism, Payne worked at S.T.A.R. Labs searching for a cure. He obtained a sample of the then-living Matt Hagen's blood, and isolated an enzyme which he introduced into his own bloodstream. Although he was briefly able to shape his own appearance, this effect was short-lived: while on a date, his flesh began to melt, and when he touched his horrified girlfriend, she completely melted. Payne built an exoskeleton anti-melting suit to prevent himself from touching anyone, but he learned that he needed to spread his melting contagion onto others to survive (he feels pain if he doesn't melt anyone). During this time his mental health started to slip as he fell in love with a wax mannequin he named "Helena", thinking she was the only woman immune to his touch.
Sondra Fuller
The fourth Clayface, Sondra Fuller, also known as Lady Clay, first appeared in Outsiders (volume 1) #21. She was an agent of Kobra who was transformed into a shape-changer by her employer's technologies. She possesses identical abilities to those of Matt Hagen, but without the requirement for a source of protoplasm. She was defeated by the Outsiders.
Cassius "Clay" Payne
After the Mud Pack, Payne and Fuller fell in love and eventually became recluses and had a child together named Cassius "Clay" Payne, who became the fifth Clayface. The boy is separated from his parents and held in a government laboratory. The full extent of his powers are unknown. The name "Cassius" is a pun on "Cassius Clay", the birthname of legendary boxer Muhammad Ali.
Claything
The sixth Clayface, also known as Claything, was created when a skin sample from Cassius Payne came to life and merged with a DEO (Department of Extra-Normal Operations) scientist, Dr. Malley. He had the ability to melt objects simply by looking at them. Claything was destroyed and his remains are stored at the DEO HQ. These events took place in Batman #550: "Chasing Clay".
Mud Pack
Before the appearance of the fifth and sixth Clayfaces, the third and fourth Clayfaces teamed up, breaking the original Clayface out of prison and forming the Mud Pack. Karlo later managed to copy the others' powers by injecting himself with extracts of samples of the other two Clayfaces, becoming the "Ultimate Clayface". The three battled and were defeated by Batman.
In other media
The original animated form of Clayface was derived from the Teen Titans comics character Plasmus.
Batman: The Animated Series
In Batman: The Animated Series, several episodes featured a more tragic Clayface character, voiced by Ron Perlman, that combined aspects of several of the comic-book Clayfaces. He was Matt Hagen, a past-his-prime actor who had been disfigured in a horrible car accident and was rushed to the burn clinic. While at the burn clinic, he was approached by corrupt businessman Roland Daggett and had him turned to an untested, non-FDA approved, and highly addictive, cosmetic compound called Renuyu to maintain his youthful appearance compared to years of plastic surgery. In exchange, Hagen would commit crimes for him. When Hagen stopped, his supply was cut off. He was caught in Daggett Industries trying to steal a large supply of Renuyu by Raymond Bell and Germs, who worked for Roland Daggett; they then tried to kill him by forcing him to ingest an entire canister of Renuyu. Rather than kill him, however, the overdose saturated every cell in his body, turning him into a bulky and misshapen claylike form who could, for short periods of time, shapeshift into anything or anybody he wished. After trying to get revenge on Daggett, he was stopped and, apparently, destroyed by Batman. It was soon discovered that he had faked his own death, however, and was still very much alive for the time being.
Eventually, Clayface began to slowly fall apart as his chemical structure degraded. He took refuge with a young, female research scientist who fell in love with him and helped him commit crimes to afford the research necessary to find a cure. Just as they were in the middle of administering a treatment, however, Batman intervened and fought him. Beaten, Clayface essentially committed suicide by allowing himself to fall into the nearby ocean.
About a year later, however, Clayface revealed that he had been able to survive this experience when his dissolving remains drifted by a sewer pipe depositing industrial waste into the ocean. Something in the chemicals allowed him to keep enough of himself together until he took refuge in the Gotham reservoir system. He soon displayed the ability to form automata from his body to be sent to do things for him at a distance. Robin encountered one, a young girl who had no memory of her origin and developed an independent personality. In time, Clayface sought to reabsorb her, fighting Robin to get to her. As Clayface was just about to kill the hopelessly overmatched Robin, the automaton sacrificed herself to save him by ramming and absorbing herself into her maker, knocking him into the sewer. Although Clayface was captured and arrested, Robin complained he should be charged with murder for the automaton's fate.
Justice League
Clayface made his return to action in the Justice League series, where it was revealed that at some point, he had been captured, separated and sealed into several biohazard canisters, which came into the possession of a wealthy collector named Morgan Edge. Gorilla Grodd and his newly-formed Secret Society attacked his mansion, freeing Clayface and offering him a position in their group. Grodd promised Clayface that he'll find a way to revert Clayface back to Matt Hagen. Clayface was defeated when the Flash planted fireworks in his clay body and Hawkgirl ignited them, blowing Clayface apart. It is unknown whether he survived or not.
The Batman
In The Batman, Clayface was Detective Ethan Bennett, a detective in the police force, and Bruce Wayne's friend basketball buddy from high school. Bennett was a great supporter of the Batman.
Clayface originated in the two-part episodes "The Rubber Face of Comedy/The Clay Face of Tragedy." After he inhaled a dose of Joker's Joker Putty, Bennett was rescued by Batman and his partner, Detective Ellen Yin. He was suspended by Chief Rojas after publicly denouncing the chief's claims about the Batman. At his apartment, Bennett mutated into a featureless gray-clay like figure, and tried to look for help, scaring away the locals. Clayface had become obsessed with killing Chief Rojas.
Batman and Yin found the connection that Clayface was Ethan Bennett. At East Gotham Gym, Chief Rojas was almost killed by Clayface, but Batman rescued him, and a confrontation ensued. In the end, Clayface turned into a puddle, washing down the locker room drain.
In Meltdown, Clayface is getting a payback against the Joker for his transformation, and he was captured by Batman using a freeze pellet. After Bennett was released from Arkham Asylum on probation during a trial where a scientist and Hugo Strange protested against Bruce Wayne's suggestion, he still wanted to get his revenge on the Joker during the time he was a security guard. At the confrontation, Clayface becomes a criminal and he was sent to Arkham after getting away from Batman only to get captured by Ellen Yin who uses a freeze pellet where he resides at his cell.
In Grundy's Night, Clayface disguises himself as Solomon Grundy to terrorize people on Halloween. In the wax museum, Batman confronts Clayface. In the end, Clayface was encased in wax, and he was taken back to Arkham Asylum.
This version of Clayface was voiced by Steve Harris.
A new Clayface (presumed to be Matt Hagen) will his debut on The Batman.
Arkham Asylum
A stunted, emaciated Clayface III appears in the graphic novel Arkham Asylum by Grant Morrison and by Dave McKean, where he is used as a metaphor for AIDS.
Birds of Prey
Clayface also made an appearance in the last episode of the short-lived Birds of Prey television series. In this series he killed Catwoman and had a son named Chris.
Other
The Mask animated villain Putty Thing was a clear parody of Clayface from The Animated Series, albeit portrayed as a dumb surfer teenager. Putty Thing had the same abilities to create weapons. He never shape shifted to look human, though as the character was portrayed as being incredibly stupid, he may have simply been unaware of his own abilities.