List of The Big Bang Theory episodes

This is a list of episodes from The Big Bang Theory, an American comedy television series created and executive produced by Chuck Lorre and Bill Prady.

The series is about two socially inept prodigies, Leonard Hofstadter (Johnny Galecki), and Sheldon Cooper (Jim Parsons), who are living across the hall from a beautiful but average girl, Penny (Kaley Cuoco). When Leonard falls for Penny, Sheldon tries to discourage his interest because he believes his friend is chasing a dream he'll never catch.

With the exception of the pilot, the episode titles of The Big Bang Theory always start with "The", reference a minor plot point in the episode, and typically resemble the title of a scientific principle.

Series overview

Season		Episodes	Originally aired	DVD release date	DVD Discs	Season Premiere	Season Finale	Viewers (millions)	Rank	18–49 Rating/Share (rank)
	1	17	2007-08	September 2, 2008	3	September 24, 2007	May 19, 2008	8.34	TBD	3.3/9 (TBA)
	2	23	2008-09	September 15, 2009	4	September 22, 2008	May 11, 2009	10.15	TBD	3.8/10 (TBA)
	3	TBA	2009-10	TBA	TBA	September 21, 2009	TBA	TBD	TBD	TBD

Season 1: 2007-08

Physicists Leonard Hofstadter and Sheldon Cooper get their lives shaken up when an attractive young woman named Penny moves in to the apartment across the hall from theirs. Leonard begins to develop a love for Penny, while she puts up with his friends: Sheldon Cooper, who appears borderline obsessive-compulsive; Howard Wolowitz, a sex-crazed maniac; and Rajesh, who will not speak to her, as he is too shy to talk to girls. Throughout the season: Sheldon loses his job for insulting his new boss, finds his ego bruised by a child prodigy, and finds himself unable to bear being part of a lie that Leonard has told—always attacking the world with a relentless need to assert his supremacy; Rajesh learns that he can talk to girls only when he's drunk; and Penny and Leonard go out in the final episode.

Series #	Season #	Title	Directed By	Written By	Original airdate	Prod. Code
1	1	"Pilot"	James Burrows	Chuck Lorre & Bill Prady	September 24, 2007 (2007-09-24)	101
Two brilliant ("a combined IQ of 360") young physicists, Leonard and Sheldon, are the kind of "beautiful minds" that understand how the universe works. But their PhDs don't help them interact with people, especially women. All this begins to change when a free-spirited, newly single beauty named Penny moves in next door. When Leonard and Sheldon meet Penny, Leonard is immediately interested in her (saying "our babies will be smart and beautiful"), but Sheldon feels his friend is chasing a dream he'll never catch (adding "not to mention imaginary"). Sheldon is quite content to spend his nights playing Klingon Boggle with their socially dysfunctional friends, fellow geeky Caltech geniuses, Wolowitz (a wannabe ladies man) and Koothrappali (who is so shy he cannot speak to beautiful women). However, Leonard sees in Penny a whole new universe of possibilities... including love. Leonard is so infatuated with Penny that after letting her use their shower (hers was broken) he agrees to try to retrieve her TV from her ex-boyfriend, Kurt. Leonard's efforts fail when he and Sheldon, who unwillingly accompanied him, are both depantsed and left empty handed. Feeling bad, Penny offers to buy them and their friends dinner.
2	2	"The Big Bran Hypothesis"	Mark Cendrowski	Robert Cohen & David Goetsch (teleplay) Chuck Lorre & Bill Prady (story)	October 1, 2007 (2007-10-01)	102
When Sheldon and Leonard go over to Penny's apartment to drop off a package that came for her, Sheldon is deeply disturbed when he sees how messy and disorganized her apartment appears. Later that night, when Leonard is sleeping, Sheldon sneaks into Penny's apartment to clean and organize it. Leonard catches him and tries to stop him, but gives up and helps him to clean up in the end. The next morning, Penny yells at them, prompting Leonard to ask Sheldon how she knew (Sheldon had left an organizational diagram for her closet). Sheldon apologizes to Penny but fails after remarking that Leonard is a "thorough and gentle lover." Later, Penny encounters Raj in the hallway and chats with him, finally realizing that the guys were just trying to help her. Leonard then apologizes, prompting Penny to hug him and say 'We're okay'. The title refers to Sheldon switching his type of cereal to a higher fiber content after Penny screams when she finds out her apartment has been rearranged.
3	3	"The Fuzzy Boots Corollary"	Mark Cendrowski	Steven Molaro & Bill Prady (teleplay) Chuck Lorre (story)	October 8, 2007 (2007-10-08)	103
When Leonard sees Penny kissing a guy in front of her apartment door, he is devastated thinking she has 'rejected' him. The guys convince him to ask someone out at work, but when he tries and is brutally turned down by a geeky girl scientist named Leslie Winkle (Sara Gilbert), he is even more depressed. As Leonard slips deeper into his depression (which involves thinking about buying a cat and listening to emo music), Sheldon (in an attempt to not have a cat) points out that he was not actually rejected, as he had not asked Penny out. Leonard agrees and promptly asks Penny out to dinner, but she mistakes his invite as an invitation to hang with all the guys. Despite being aware of this, Leonard keeps the date and makes up excuses as to why the guys were absent. On the date, Penny mentions the man Leonard saw was not her boyfriend, but that she has a habit of having weekend long flings to get over relationships. Excited, Leonard begins to become more confident but, after accidentally hurting himself, the date becomes a disaster and Penny takes him home. Leonard does not get the courage to reveal his true feelings to Penny, even though she suspected what he was up to. The title refers to names Leonard was going to name his cat.
4	4	"The Luminous Fish Effect"	Bob Koherr	David Litt & Lee Aronsohn (teleplay) Chuck Lorre & Bill Prady (story)	October 15, 2007 (2007-10-15)	104
Sheldon is fired from his job as a physicist at the university when he insults his (in his opinion less-gifted) new boss Dr. Eric Gablehauser (Mark Harelik). His change of circumstance sends him into a downward spiral of depression which Leonard tries to cure by sending for Sheldon's mom (Laurie Metcalf). When she arrives for a visit, the boys realize she is completely the opposite from what they expected. She is down-to-earth, sweet, and a devout Christian ("All that science stuff comes from Jesus"). After waiting it out his mother finally forces Sheldon to apologize and he is given his job back, after she flirts with Dr. Gablehauser (she is apparently widowed). Sheldon asks if Dr. Gablehauser will be his new daddy and his mother replies, "We'll see..." The title refers to Sheldon creating glow-in-the-dark fish during his period of unemployment.
5	5	"The Hamburger Postulate"	Andrew D. Weyman	Steven Molaro & David Goetsch (teleplay) Jennifer Glickman (story)	October 22, 2007 (2007-10-22)	105
While eating at The Cheesecake Factory where Penny works, the guys run into Leslie Winkle (Sara Gilbert), a fellow scientist who works with Leonard (and previously turned him down for a date saying she had no attraction to him). She suggests that Leonard play in her string quartet as they are in need of a new cellist. However, what she really wants is to get personal with Leonard (especially after hearing him play the cello). When Sheldon comes home and finds a necktie on Leonard's door, he runs to Penny’s apartment to ask her what the necktie means. Penny tells him and seems slightly disappointed, though she does congratulate Leonard later on. Leonard tries to figure out what her words meant, but eventually gives up, deciding he should choose a real relationship (Leslie) over an imaginary one (Penny). However when he arrives in the lab, Leslie makes it clear she used him just to satisfy her sex drive, saying she's 'good till New Year's'. Leonard later tells Penny, who walks away with a smile on her face; she seems to be quite happy to hear this news. The title refers to Sheldon switching his favorite burger restaurant.
6	6	"The Middle Earth Paradigm"	Mark Cendrowski	Robert Cohen & David Litt (teleplay) David Goetsch (story)	October 29, 2007 (2007-10-29)	106
The guys are invited to Penny's Halloween party, first turning it down as they "don't dance" but changing their mind when costumes are mentioned. Once at the party, only Wolowitz and Leonard attempt to socialize - with mixed success. Penny's ex-boyfriend Kurt shows up and humiliates Leonard, causing him to leave. Penny goes to check on him and apologizes. Both drunk and upset, she kisses Leonard, which he refutes with the obvious reasons as to why she's doing it. Penny says he's sweet and wonders why all men can't be like him, with Leonard replying, "Because the human race wouldn't survive". Penny goes to leave and kisses him once more in the doorway. When Penny leaves the doorway, Kurt is standing there looking stunned and angry, prompting Leonard to inform him, "that's right, you saw what you saw, that's how we roll in the shire" (as he was dressed as Frodo Baggins). Leonard quickly locks the door to his apartment with a satisfied smile. Meanwhile, Wolowitz can not find Koothrappali, who ends up going home and has sex with a girl he had met at the party, who found him to be a 'good listener' (as Koothrappali is so shy he can not speak to attractive women). The title refers to Leonard's Halloween costume; he dressed up as Frodo.
7	7	"The Dumpling Paradox"	Mark Cendrowski	Lee Aronsohn & Jennifer Glickman (teleplay) Bill Prady & Chuck Lorre (story)	November 5, 2007 (2007-11-05)	107
Penny's promiscuous 'friend' Chrissy (Brooke D'Orsay) from Nebraska is in town, and ends up being seduced by Wolowitz. The pair take over her apartment causing her to sleep on Leonard and Sheldon's couch for the night. With Wolowitz gone, Penny takes his place on their Halo team, causing Sheldon much distress as she is naturally good at it. Chrissy moves in with Wolowitz (and his mother) taking up all his time. Sheldon is distraught over the odd number in the group believing they can no longer function. He's even more distraught when he relents and lets Penny join in on Halo night, but she declines the offer to go dancing with her friend instead. Believing that they are falling apart as a group, the guys go to speak to Wolowitz. When they arrive they hear Chrissy and Wolowitz's mother arguing loudly, causing Chrissy to leave. Wolowitz, once again single, says 'So, Halo night?' and the group is restored. The title refers to the scene where Leonard, Sheldon, and Raj are at the Chinese restaurant and do not know what to do with an extra dumpling (which Wolowitz normally would have eaten).
8	8	"The Grasshopper Experiment"	Ted Wass	Robert Cohen & Lee Aronsohn (teleplay) David Goetsch & Steven Molaro (story)	November 12, 2007 (2007-11-12)	108
Koothrappali is overwhelmed after his parents arrange a blind date with a girl from his childhood, as he cannot talk to attractive members of the opposite sex. Penny takes up bar tending for some extra money; and as she practices mixing drinks with the guys they discover that after a few drinks Koothrappali can actually talk to women. However on his date at Penny's restaurant (with all the guys watching from the bar), he becomes obnoxious, and the girl ends up leaving with Sheldon after he accidentally complimented her by comparing her to a beautiful Indian fairy tale princess. Koothrappali and Leonard return to Leonard's apartment where Koothrappali tries to explain to his parents what happened. Even though he is already upset things become worse when his parents find out he was drinking and he gets lectured and has to leave the apartment. Sheldon returns and Leonard asks him what happened after the pair had left the bar. Sheldon seems to not have thought of it as a date, implying he will not see her again (making Leonard wonder out loud, "I wonder who will tell his parents they're not getting grandchildren"). The title refers to the drink (a Grasshopper) that enabled Raj to speak to women.
9	9	"The Cooper-Hofstadter Polarization"	Joel Murray	David Goetsch & Chuck Lorre & Lee Aronsohn (teleplay) Bill Prady & Stephen Engel (story)	March 17, 2008 (2008-03-17)	109
Cleaning up after an internet experiment, Leonard discovers a letter in the trash can. He and Sheldon had been invited to present some research they had done together at a physics conference. However Sheldon does not believe in such things and says if he won't go, no one can. Leonard defies him and says he will go and present the findings on his own. This causes a rift between the two which Penny tries to mend but accidentally makes worse. At the conference Sheldon appears and not only tries to "blow up" Leonard's head with his mind a la the movie Scanners, but has a physical altercation with Leonard. In the end, the fight is captured by Wolowitz and put on YouTube. The title refers to the research both Leonard and Sheldon came up with.
10	10	"The Loobenfeld Decay"	Mark Cendrowski	Bill Prady & Lee Aronsohn (teleplay) Chuck Lorre (story)	March 24, 2008 (2008-03-24)	110
Penny was given a part in Rent, though after hearing her sing "Out Tonight" extremely off-key ("What the hell is that?" "I don't know, but if cats could sing...they'd hate it too.") Leonard lies to avoid seeing her performance so he won't hurt her feelings. Sheldon becomes paranoid that Leonard's lie was 'laughably transparent' and eventually creates an intricate lie about his non-existent drug addicted cousin Leo, who was in need of an intervention (and thus why they could not see the play). Sheldon becomes so obsessed he actually has a fellow physicist (who double majored in theatre) play the cousin to convince Penny that the lie is true. In the end, Leonard still has to see the tape of Penny's performance, the lie doing him no good at all. The title refers to the name of the physicist/actor, which was Toby Loobenfeld (played by DJ Qualls, best known for his role as Kyle from the movie Road Trip).
11	11	"The Pancake Batter Anomaly"	Mark Cendrowski	Bill Prady & Stephen Engel (teleplay) Lee Aronsohn & Chuck Lorre (story)	March 31, 2008 (2008-03-31)	111
Penny returns from visiting family in Nebraska, and as she picks up her mail from Leonard, she mentions it was a bad trip because 'everyone got sick'. Sheldon freaks out as according to Leonard 'he's a bit of a germaphobe'. Sure enough, Sheldon becomes sick and instantly becomes the biggest pain possible; it seems that this has happened before. Leonard and the guys hide from him at a Planet of the Apes marathon, leaving Penny unwillingly to take care of Sheldon. However, Leonard accidentally breaks his glasses and must re-enter the apartment, where Penny catches him and sticks him with Sheldon. In the end, both Leonard and Sheldon are sitting sick and injured on the couch. Sheldon wonders if Penny will come take care of them, to which Leonard replies, "I don't think Penny is ever coming here again." The title refers to Sheldon's urine sample measuring cup, which turned out to be the same cup Leonard uses to mix pancake batter.
12	12	"The Jerusalem Duality"	Mark Cendrowski	Steven Molaro & David Goetsch (teleplay) Stephen Engel & Jennifer Glickman (story)	April 14, 2008 (2008-04-14)	112
Sheldon is overcome with I.Q. envy when he meets a smarter 15-year-old science prodigy named Dennis Kim (Austin Lee). Losing faith in his own research, he annoys his circle of friends and colleagues by visiting them and criticizing their work (prompting them to say "Go away!" whenever he's around). Deciding his work in physics is useless, he decides to aim for the Nobel Peace Prize by creating a 'Nuevo Jerusalem' for the Jewish people in the Mexican desert (thus creating peace in the Middle East). The guys, tired of his insults and his craziness decide to take Dennis out of the picture by getting him distracted with girls. At his welcome party, their plan works (though mostly by accident) and Dennis leaves with a blonde 15 year old (Unfabulous's Emma Degerstedt) for the mall. Excited, Sheldon declares his work will continue on and “social relationships will continue to baffle and repulse me.” The guys were excited Sheldon was back to his old self, but Leonard, Wolowitz and Rajesh were upset and perplexed at how Dennis was able to get girls while they were not when they were his age. Eventually they conclude that they are too smart and it repels women (to which Wolowitz says "Yeah, let's go with that.") The title refers to the proposed duplication of Jerusalem and may be a pun on the wave-particle duality concept.
13	13	"The Bat Jar Conjecture"	Mark Cendrowski	Bill Prady & Robert Cohen (teleplay) Stephen Engel & Jennifer Glickman (story)	April 21, 2008 (2008-04-21)	113
The guys decided to compete in a physics bowl after finding out that the previous competitors have dropped out to form a barbershop quartet and got a gig playing Knott's Berry Farm. However, they find Sheldon's showboating too much and kick him off the team, telling him "You're annoying and no one wants to play with you", despite the fact that he was reluctant to compete in the first place. They even buy him a Batman cookie jar to soften the blow of being cut from the team. Upset, Sheldon vows to form his own team and compete against them. The guys, in need of a 4th member, ask Leslie Winkle to join them. She rejects the offer at first, but after being told the purpose of their team is to defeat Sheldon, she joins in as Sheldon had once told her that she should give up her research to bear children and do laundry, or so she said. At the bowl, the guys team is called PMS, for Perpetual Motion Squad ("We can go all night!"). Sheldon assembles the 3rd floor janitor, the lunch lady, and her son (or butcher) as he could not compete alone. Sheldon's team is named AA for Army Ants. PMS wins by one question, when Sheldon (unable to answer the question) won't let Dr. Gablehauser accept the janitor's answer, -8πα, even though it turns out to be correct. The janitor proceeds to explain that in America, he is a janitor, but in the former Soviet Union, he was a physicist. In the end, Penny declares she will tell who is officially the smartest by asking a bunch of pop culture questions. Despite having a "combined IQ of 360", neither of the boys is able to answer any of the questions. The title refers to the Batman cookie jar ("Bat Jar") given to Sheldon.
14	14	"The Nerdvana Annihilation"	Mark Cendrowski	Stephen Engel & Steven Molaro (teleplay) Bill Prady (story)	April 28, 2008 (2008-04-28)	114
This episode was originally titled The Nerdmabelia Scattering. Online, Leonard buys a replica time machine from the 1960 film, The Time Machine, believing it to be a miniature... though it turns out to be full-sized. As the boys move it into the apartment, they accidentally make Penny late for work causing her to lash out at Leonard for his nerdy ways. Upset, Leonard decides to get rid of all his collectibles and the guys try to convince him not to (or sell them to them, whichever). In the end, Sheldon confronts Penny about her own love of childish things (Hello Kitty, Beanie Babies, My Little Pony, etc.) and she apologizes to Leonard. However, she has a new boyfriend named Mike, and once Leonard finds this out, he reverts to his old ways. The title refers to Howard's referring to Leonard and Sheldon's place as "Nerdvana" because of the collection of geeky items in their apartment.
15	15	"The Pork Chop Indeterminacy"	Mark Cendrowski	Bill Prady & Lee Aronsohn (teleplay) Chuck Lorre (story)	May 5, 2008 (2008-05-05)	115
The episode is sometimes called The Shiksa Indeterminacy. The guys see an attractive woman in Sheldon's office and cannot believe their eyes. The woman turns out to be his twin sister Missy (Courtney Henggeler), who was in town for a wedding and needed Sheldon to sign some papers for their father's estate. The boys are smitten with her and Leonard insists she stay with them. The boys instantly try to hit on her, causing Penny to come to her rescue. Meanwhile, Leonard becomes sneaky and convinces Sheldon to be protective of Missy (so he can have a chance at her over the other guys) … however, much to Leonard's chagrin, Sheldon forbids him to go out with his sister as well. Upon learning what Sheldon is up to, Missy has a heart-to-heart with Sheldon and, after getting crotch-punched by Missy, Sheldon agrees "Missy can date whoever she wants". After a Wii Boxing battle Leonard wins first chance, but Missy turns him down (something they had apparently not expected). Wolowitz tries next, but she turns him down as well. Meanwhile, Koothrappali takes part in a drug trial, for a drug that can cure his extreme shyness and inability to talk to attractive women. It works (with side effects), but when it comes to asking Missy out the drug wears off and he is unable to speak to her, forcing him to leave defeated. Adding insult to injury, it seemed Missy would have given him a chance, saying when she answered the door that she was 'hoping he'd show up'. The title refers to Howard saying he'd kill his rabbi with a pork chop to be with Missy, who wasn't Jewish (hence a shiksa), therefore unsuitable for Wolowitz.
16	16	"The Peanut Reaction"	Mark Cendrowski	David Goetsch & Steven Molaro (teleplay) Lee Aronsohn & Bill Prady (story)	May 12, 2008 (2008-05-12)	116
When the boys dine at Penny's restaurant, she learns Leonard has never had a birthday party, as his parents didn't believe in celebrating anything but achievements. She decides to throw him a surprise party, and blackmails Sheldon to join her. However when the day of the party arrives, she finds Sheldon did not buy a birthday gift. After some help from Wolowitz in convincing him it was a 'non-optional social convention', Penny drives Sheldon to a computer store where he becomes distracted, helping other customers with their tech-related questions. Meanwhile, Wolowitz is in charge of keeping Leonard busy until the party. After Wolowitz pretends to eat a peanut bar (to which he is allergic), Leonard drives him to the emergency room. Due to Sheldon's absent-mindedness, Wolowitz has to keep Leonard distracted even longer, and after a promise from Penny of "being shown which of her friends is easy", Wolowitz actually eats the peanut bar...causing him to swell up in an allergic reaction. After being at the hospital for several hours (in which they tested everything for fear of being sued), Wolowitz and Leonard arrive back at the apartment to find Penny asleep on the couch, Sheldon asleep in the chair, and Koothrappali drunk singing karaoke telling them everyone left an hour ago. In the end, Penny shows Leonard a cell phone video of the party and ends up giving him a kiss. The title refers to Wolowitz's allergy to peanuts.
17	17	"The Tangerine Factor"	Mark Cendrowski	Chuck Lorre & Bill Prady & Steven Molaro & Lee Aronsohn	May 19, 2008 (2008-05-19)	117
Penny breaks up with her boyfriend after he posted intimate details about her on his blog. Leonard goes to comfort her and in doing so accidentally convinces her to get back with her boyfriend. As Leonard laments the situation to the guys, Penny returns and screams at Leonard, saying he made things worse. He tries again and she apologizes; saying it wasn't his fault. She explains that when she went over to make up, she found her boyfriend had already moved on. As Penny laments her choices in men, Leonard awkwardly asks her on a real date. Penny thinks for a moment and agrees saying, "Sure, why not?". A few days pass and both Leonard and Penny are worried that this date will ruin their friendship. They both seek Sheldon's advice. Sheldon advises Penny that “just like Schrödinger's cat being alive or dead at same time” her date with Leonard currently has both “good and bad” possible outcomes. The only way to find out is to “open the box”, or in other words to go on the date and find which outcome it is. Leonard is also given the same advice, and understands it right away. When Leonard arrives to pick Penny up for their date, she says they need to talk. Leonard asks her if she has ever heard of Schrödinger's cat and when she says she has, he passionately kisses her. Penny says "the cat's alive" and they leave for dinner. Meanwhile, Sheldon asks Wolowitz to teach him Mandarin as he's convinced the Chinese restaurant is selling 'Tangerine Chicken' yet is really using oranges, a cheaper citrus. He doesn't become very good at it, and as a result the owner (James Hong) thinks he's crazy due to his humorous mistranslations (such as "Show me your mucus!", "This is not a tangerine bicycle!", and "Oxen are in my bed! Many, many oxen!"). It appears Leonard and Penny were going to go to this restaurant on their date, but when they see Sheldon fighting with the owner, they leave before entering. The title refers to the Chinese Tangerine Chicken which Sheldon believed was actually prepared with oranges.

Season 2: 2008-09

Season Two begins to deal with character development, including Sheldon becoming more and more obsessive, with a characteristic lack of understanding of irony and sarcasm reminiscent of Asperger syndrome. Leonard and Penny's relationship takes a turn for the worse when they break up, but quickly is resolved. Soon their relationship progresses into a stronger friendship than before, while Sheldon and Penny's friendship slowly begins. In the season finale Penny hints at her true feelings for Leonard. Howard's character remains similar to that of season one in his attempts to seduce women, while Rajesh manages to briefly apologize to Penny without having consumed alcohol.

Series #	Season #	Title	Directed By	Written By	Original airdate	Prod. Code
18	1	"The Bad Fish Paradigm"	Mark Cendrowski	Bill Prady, Steven Molaro & David Goetsch	September 21, 2008 (2008-09-21)	201
Penny and Leonard return from the restaurant while Howard and Rajesh spy on them, using a webcam on the corridor connected to a laptop. Out of obvious envy, they try to convince Leonard that the date didn't go well, leading Leonard to question where he went wrong. On the other hand, after Penny and Leonard's date, Penny feels uncomfortable having not completed community college. She is afraid that Leonard would become bored with her. She lied to Leonard about completing her own college and makes Sheldon keep her secret. This request to deceive Leonard is very hard for Sheldon (and his nervous tics) and results in the drastic decision on Sheldon's part to move out. However, after moving from Raj's and Howard's homes (in the course of one night) and refusing to sleep, even after Howard gave him "a glass of warm milk with a handful of my mum's Valium in it," Sheldon is brought back home by Howard, where he admits Penny's failure to complete community college. Leonard, in an attempt to help Penny, offers her some pamphlets regarding some local community colleges, claiming he's okay with dating a girl "who isn't smart." She promptly slams the door in his face. Leonard remarks, "Okay, this time I know where I went wrong," and he finds Wolowitz and Koothrappali eavesdropped on the whole incident via the webcam. The title refers to Wolowitz calling Leonard a "bad fish" and Leonard later realizing it.
19	2	"The Codpiece Topology"	Mark Cendrowski	Chuck Lorre, Bill Prady & Lee Aronsohn	September 28, 2008 (2008-09-28)	202
The guys return from a Renaissance fair (which gives the episode its name) and see Penny with a new guy, Eric (Travis Schuldt), prompting a jealous Leonard to pursue a relationship with fellow physicist Leslie Winkle. All the guys as well as Leslie humiliate Leonard for his apparent failure to keep Penny. Leslie eventually agrees to date Leonard, repeatedly assuming the dominant role before conceding that he should "assume the male role". Leonard convinces Sheldon to leave the apartment, to give his roommate and Leslie some privacy. On the staircase, while playing Super Mario 64 "on a poorly-coded Nintendo 64 emulator", Sheldon explains to Penny that he feels uncomfortable with Leonard dating his arch enemy, Leslie, who is a "sloppy, arrogant, sub-par scientist". Sheldon returns to their apartment and formally approves the relationship between Leonard and Leslie, graciously overlooking that she actually believes loop quantum gravity instead of string theory. Leslie gets emotional and makes statements about Lorentz invariance and black hole entropy which Sheldon scoffs at. Leslie expects Leonard to back up her beliefs but finds that he shares Sheldon's instead. Leslie then asks how they should raise the children as if it were a decision to raise their children in one religion or another. After learning about this "deal breaker," which she believes is more serious than Leonard's food allergy and shortness, she breaks up with him. The title refers to Sheldon stating that the Renaissance Fair was a "Medieval/Age of Enlightenment/any-excuse-to-wear-a-codpiece fair".
20	3	"The Barbarian Sublimation"	Mark Cendrowski	Nicole Lorre, Steve Molaro & Eric Kaplan	October 6, 2008 (2008-10-06)	203
Sheldon becomes distracted from playing Age of Conan by Penny who has accidentally attempted to use her car keys to open her apartment door. Sheldon learns that Penny is frustrated by her failures in life specifically her not getting into any of the parts in plays she's tried out for, not having sex for six months, not receiving a raise at work and, on her way up the stairs, she swallowed a fly. Sheldon invites her into his apartment to wait until the locksmith arrives to open her door. Penny becomes curious about the game Sheldon is playing and quickly becomes addicted. They quickly try to help her regain her regular life back as they try to set her up with an online dating service which failed miserably. After falling deep into her addiction, she inadvertently accepts an online date consisting of questing and drinking ale at the local virtual tavern with Howard. She quickly realises what she's done and promptly stops playing the game as the episode ends. The title refers to Sheldon and Penny playing Age of Conan (Conan the Barbarian) as the characters "Sheldor, The Conqueror" and "Queen Penelope", respectively, and to the psychological concept of sublimation - transformation of sexual energy into non-sexual endeavors (in this case, into online gaming).
21	4	"The Griffin Equivalency"	Mark Cendrowski	Chuck Lorre, Bill Prady, Stephen Engel & Tim Doyle	October 13, 2008 (2008-10-13)	204
Raj is included in People magazine's '30 Under 30 to Watch' list for his discovery of the trans-Neptunian object 2008 NQ17, sparking jealousy from his friends: Wolowitz received no mention of his mechanical design that led to Raj's discovery, and Sheldon doesn't understand why Raj's stroke of luck (being the first to recognize an already-existing celestial object) is worthy of any recognition. Leonard admonishes them and they attempt to be supportive of Raj, but fame soon goes to his head: he receives star treatment from Gablehouser, gets an assistant and gives misleading interviews about his 'humble background' (his father is a gynecologist and drives a Bentley). Leonard, still having been supportive, loses his cool when Raj asks Penny to be his date for the party thrown by People, followed by the snide comment of, "I can't believe it took you a year." After the party, a very intoxicated Raj and annoyed Penny return to his apartment (The 'Raj Mahal') and receive a web-call from his parents, who criticize Raj for 'dating' a white girl despite Penny setting them straight that she isn't his girlfriend. The night ends when Raj exits to be sick from drinking too much at the party. The following morning, Raj appears sober and hungover on Penny's doorstep and she makes him apologize to her without any notes or third-party interpretation. This leads to Raj's first ever direct words to Penny while not drunk or distracted - 'Sorry'. She gives him a hug, showing her forgiveness, at which point Leonard leaves his apartment and sees them hugging. When Penny leaves, Raj turns around and gives Leonard a gloating grin. Sheldon comes out and closes the episode by giving an over-forced smile he used throughout the episode. This episode also includes a cameo from Charlie Sheen; at Penny's restaurant after the guys all leave, Raj says to the patron at the next table over, "Hey, buddy. I'm going to be in People magazine!", Sheen turns around and says "Yeah? Call me when you're on the cover." The title refers to Sheldon wishing to have a griffin as a perfect pet, an anecdote he used to propose that the gang adopt a new fourth (i.e., the equivalent of the "perfect pet"). However, once Leonard totes up their criteria (access to a great house, high technology and lots of women), he comes to the conclusion that their new friend is going to be Iron Man.
22	5	"The Euclid Alternative"	Mark Cendrowski	Lee Aronsohn, David Goetsch, Steven Molaro & Bill Prady	October 20, 2008 (2008-10-20)	205
Leonard is working nights on an experiment - the lasers he needs are only available on the graveyard timeslot - resulting in his inability to drive Sheldon to the university. As a result, Sheldon must find another way to get to work, which includes invoking a favor from Penny on her day off from the restaurant and a return trip from Wolowitz on his scooter and Raj being forced to pick Sheldon up after both eject him from their respective vehicles. The friends finally stage an intervention and tell Sheldon he must get his driver's license because he should be taking on the responsibility of driving himself to work (and so he will stop bothering them for rides). After an eventful trip to the Department of Motor Vehicles, resulting in Sheldon circumventing the test procedure by annoying the DMV worker, the gang sets up a simulation for him in the living room. The ensuing practice shows the gang that both the simulation was a great idea as opposed to an actual trip in a car and why Sheldon never learned to drive in the first place - he's a horrible driver. Later, despite actually having a license, Sheldon decides to forgo using it and instead moves into his office for the duration of Leonard's night shifts. However, Leonard slyly neglects to inform him of the actual end date, resulting in Leonard living in peace in the apartment for an extra week as the episode folds. The title refers to the Euclid Avenue that Sheldon is afraid of passing through on his way to work.
23	6	"The Cooper-Nowitzki Theorem"	Mark Cendrowski	Stephen Engel, Daley Haggar, Tim Doyle & Richard Rosenstock	November 3, 2008 (2008-11-03)	206
After an open house night with grad students, a particularly obsessive grad student named Ramona Nowitzki (Riki Lindhome) takes a shine to Sheldon and insinuates herself into his life and work as a girlfriend/assistant. However, Sheldon remains oblivious to her intentions, leaving the gang doubly confounded. She proves to be a positive and helpful influence on his life...until she begins to cut off his social life - no more Halo night, paintball, comic books or Battlestar Galactica. Ramona also goes so far as to presume that Penny has a crush on Sheldon when she sees them talking together in the hallway adjoining their apartments. Sheldon finally realizes that he's in a "relationship" with Ramona and seeks help from Leonard to get rid of her. Things come to a head when the gang comes into the apartment and see that Sheldon's solved his scientific problem that Ramona made him work on day and night until he solved it, and when Ramona suggests they share credit for his discovery - calling it the 'Cooper-Nowitzki Theorem', which is what the title refers to - Sheldon's response is 'Get out!'. Things seem to go back to normal until Sheldon is approached by another young woman in the same way Ramona approached Sheldon first, and the episode folds as the cycle begins again. This episode also features the first montage sequence in the series. The music is "Be My Yoko Ono" by the Barenaked Ladies.
24	7	"The Panty Piñata Polarization"	Mark Cendrowski	Jennifer Glickman & Steven Molaro (teleplay) Bill Prady & Tim Doyle (story)	November 10, 2008 (2008-11-10)	207
When Penny's cable gets cut, she starts coming over to the guys' apartment to watch America's Next Top Model. However, after Sheldon bans her from the apartment for a series of petty infractions (touching his food, sitting in his spot, and sending him "email humor"), Penny taunts him at the Cheesecake Factory. After a series of escalating pranks, including Sheldon cutting off Penny's access to WiFi and Penny wrecking Sheldon's laundry night by having all the washers occupied at the exact time he does his laundry, Sheldon goes to the extreme of hanging her laundry from a telephone wire outside the apartment. Penny gets her revenge after Leonard gives her Sheldon's Kryptonite--his mother's phone number. Sheldon's mother calls him and forces him to apologize to Penny. Meanwhile, Howard and Raj are trying to find the location of the Next Top Model house. They use all of the technology at their disposal, as well as a military spy plane and NASA satellites to finally pinpoint it. They arrive at the house posing as cable guys and work their way in. The episode ends as we're left to wonder what happens next. Analeigh Tipton and Samantha Potter of Cycle 11 guest star. The title refers to Sheldon taking revenge on Penny by hanging her laundry from a telephone wire outside the apartment and taunting her to play Panty Piñata.
25	8	"The Lizard-Spock Expansion"	Mark Cendrowski	Jennifer Glickman, Bill Prady & David Goetsch	November 17, 2008 (2008-11-17)	208
A smitten Wolowitz thinks he's found his soul mate--until the woman, Dr. Stephanie Barnett (Sara Rue), meets Leonard. Wolowitz invites Stephanie to drive the Mars rover, which winds up stuck in a ditch. Eventually, to hide evidence of what he has done, Wolowitz destroys all the security tapes and hard drives he can find relating to the Mars Rover mission. Leonard has a hard time deciding how to break the news to Howard that he is dating Stephanie. Sheldon, of course, is no help. Leonard decides to go to Howard's house to tell him himself. While there, Stephanie calls Howard and gives him the news. Howard tells Leonard "you are dead to me," which lasts until Stephanie invites Howard on a double-date. At the end of the episode, Wolowitz hears the news on TV that the Mars rover has found life on Mars in the bottom of the ditch, but as so much data has been mysteriously lost no one will ever know who made the amazing discovery. The episode closes with Wolowitz remarking "Son of a bitch!" The title refers to Sheldon proposal to use Sam Kass's expanded form of the game Rock-paper-scissors, called Rock-paper-scissors-lizard-Spock.
26	9	"The White Asparagus Triangulation"	Mark Cendrowski	Stephen Engel & Richard Rosenstock (teleplay) David Goetsch & Steven Molaro (story)	November 24, 2008 (2008-11-24)	209
Sheldon is concerned that Stephanie is the only girl Leonard has dated that he "finds tolerable". He tries to force himself into conversations with "urban slang" to "help" Leonard in the relationship with Stephanie, as "history suggests" he will fail ("You're [Leonard is] Kirk, I'm [Sheldon is] Spock, Wolowitz is Scottie, Koothrappali is the guy that always gets killed…and now we've got McCoy [Stephanie]"). Leonard attempts to get away from Sheldon by going to the movies with Stephanie, but Sheldon is able to follow them despite Leonard only leaving a note. ("If you were trying to make it impossible to locate you, you couldn't have done a better job." "Oh, clearly I could have.") After believing that Leonard is losing Stephanie, he runs to Penny for advice. Penny, however, is no help, so Sheldon runs to Wolowitz and Koothrappali, but all they give is, in Sheldon's words, either "apocalyptic genocide" or "go easy on the cologne". Sheldon once again runs to Penny, but she refuses to talk. Afterwards, Sheldon attempts to prove Leonard's physical superiority to Stephanie by having him open a jar of white asparagus. However, Leonard shatters the jar by accident and has to get stitches. Wondering why Leonard can't supposedly keep a date, Sheldon remarks, "You seem like a perfectly pleasant person. I can't understand why women have such a hard time loving you." Following the trip to the hospital, Leonard finds his Facebook status has been changed to "In a relationship". Leonard also finds the cause: Sheldon hacked his account, and Leonard therefore bans him from talking. It is then revealed that, in response, Stephanie has updated her own status to mirror Leonard's. Sheldon closes the episode by stating "If I am permitted to speak again, Dr. Sheldon Cooper for the win." The title refers to the content of the jar that Leonard breaks, as well as to the dysfunctional relationship "triangle" (Leonard-Stephanie-Sheldon) that features prominently throughout the episode.
27	10	"The Vartabedian Conundrum"	Mark Cendrowski	Richard Rosenstock & Bill Prady (teleplay) Steven Molaro & Chuck Lorre (story)	December 8, 2008 (2008-12-08)	210
Stephanie has moved in with Leonard and Sheldon, according to their roommate contract, though Leonard denies that she is living with them. She tries helping Sheldon with a ringing in his ear, but is unable to help him. After Sheldon walks Leonard through the changes that must be made now that Stephanie has officially moved in, Sheldon tries to have Stephanie check him more thoroughly, but Penny shows up and it turns out that neither Leonard nor Sheldon ever told Stephanie about Penny. The morning does not go well following that; Penny then proves to Leonard that Stephanie is living with him. Stephanie also buys Leonard new clothes to wear that Leonard ends up hating and eventually ruining. Realizing that his relationship with Stephanie is moving too fast for him, Leonard runs to Penny for advice. However, each time Leonard tries to follow Penny's advice to tell Stephanie how he feels, they instead end up having sex. Meanwhile, Sheldon sneaks into the hospital to test himself multiple times, as apparently the ringing hasn't stopped. By the time Leonard gets back, Stephanie has diagnosed him with an inflamed larynx, and instructed him not to speak till he gets better. The episode ends as Sheldon "asks" Penny with a computer for herbal tea & honey. The title refers to the name of boys' third-floor neighbor (Mrs. Vartabedian) who's mentioned in passing during the episode.
28	11	"The Bath Item Gift Hypothesis"	Mark Cendrowski	Eric Kaplan & Stephen Engel (teleplay) Richard Rosenstock & Bill Prady (story)	December 15, 2008 (2008-12-15)	211
Leonard meets his intellectual superior in award winning scientist David Underhill (Michael Trucco). Underhill is the total opposite of Leonard: handsome, charming, and cool. He's the whole package of brains and looks which initially doesn't sit well with Leonard. Although when Hill asks for Leonard's help in research he is undertaking, he happily jumps at the offer. Leonard's joy of working with Hill is hampered by jealousy when Underhill takes an interest in Penny and the feelings are reciprocated. However, Penny discovers that Underhill is actually married and breaks up with him. Leonard, of course, is overjoyed. Sheldon, having always viewed the holidays as a pagan ritual that is rooted in obligations rather than holiday cheer, is taken for a loop when Penny brings him a Christmas gift. He now feels obliged to buy her a gift and enlists Wolowitz and Koothrappali to help him with this task which they reluctantly agree to. Sheldon believes he has come up with the most logical gift giving scenario until he opens Penny's gift: a napkin autographed by Leonard Nimoy. Shocked and delighted at the same time, he gives her all the present options (gift baskets of various bath items) he prepared to which he claims is still not enough, and to Penny's amazement, even manages to give her a hug.
29	12	"The Killer Robot Instability"	Mark Cendrowski	Daley Haggar & Steven Molaro (teleplay) Richard Rosenstock & Bill Prady (story)	January 12, 2009 (2009-01-12)	212
When Penny's comment about Wolowitz's love life sends him into a depressed stupor, his friends lose their most important team-mate in an upcoming fighting robot competition. When Sheldon accepts a challenge for a one on one fight, pitting their robot, M.O.N.T.E. (Mobile Omnidirectional Neutralization and Termination Eradicator), against that of their co-worker, Barry Kripke (John Ross Bowie) Leonard tries to get Howard back on their team by sending Penny to apologize to him, reminding her that she owed him a favor for when he came home pantless in the Pilot episode. Penny goes to Howard's house to apologize, and ends up hearing his entire dating history. She tells Howard that if he didn't try so hard to get girls, then he would probably do much better in his relationships. After Penny's comforting words, Howard tries to kiss her, immediately followed by Penny punching him in the face. Meanwhile, M.O.N.T.E. loses to Kripke's superior robot, is destroyed beyond repair, and never enters the competition. After Sheldon organizes a vigil for M.O.N.T.E., Penny says it's "just a toy robot" and the episode folds as Sheldon sulks into his room.
30	13	"The Friendship Algorithm"	Mark Cendrowski	Chuck Lorre & Steven Molaro (teleplay) Bill Prady & Richard Rosenstock (story)	January 19, 2009 (2009-01-19)	213
Socially awkward, Sheldon develops a scientific procedure (the titular "Friendship Algorithm") for making friends. He needs to use an open science grid computer that is in Barry Kripke's office, but Leonard tells Sheldon that only Barry's friends can use it. After repeated rebuffs from Kripke, Sheldon finds a children's book in the bookstore (where he is hurried out by Leonard who finds him innocently chatting to a little girl in view of a security camera) about how to make friends. He designs a flowchart for accomplishing this task. He goes rock climbing with Kripke but faints halfway up when he sees how far he has come. Sheldon invites him over to his apartment, much to the disgust of everyone else. Raj is informed he is being replaced by Kripke as five friends would be too many to handle. Barry then tells Sheldon there is a sign-up sheet for the computer and Barry has no control over it. Sheldon then dismisses Barry as his friend and goes back to his other four friends: Leonard, Howard, Raj, and Penny.
31	14	"The Financial Permeability"	Mark Cendrowski	Richard Rosenstock & Eric Kaplan (teleplay) Chuck Lorre & Steven Molaro (story)	February 2, 2009 (2009-02-02)	214
Penny is unable to pay her rent due to an acute case of destitution, so Sheldon does the logical thing and loans her some money. Despite Sheldon's complete ease with her indebtedness, however, Penny becomes neurotic and prone to lashing out over money concerns. Leonard tries to help Penny solve her problem and in the process learns that Kurt owes Penny $1800. Without telling Penny, Leonard goes to Kurt's place to collect the money, but is sent away with "I owe Penny $1800" written on his forehead in indelible ink. At the close of the episode, Penny pays Sheldon back with money that Kurt paid her, but much to Leonard's disappointment, Kurt evidently never told Penny about Leonard's visit, and instead took the opportunity to get back together with her. The episode ends as Sheldon sings a minstrel song about Leonard (he initially said minstrels would write songs about Kurt after "triumphing" over them).
32	15	"The Maternal Capacitance"	Mark Cendrowski	Richard Rosenstock & Steven Molaro (teleplay) Chuck Lorre & Bill Prady (story)	February 9, 2009 (2009-02-09)	215
A phone call from Leonard's mother, Dr. Beverly Hofstadter (Christine Baranski, who earned an Emmy nomination for this role), leads to problems all around as childhood problems emerge from both Penny and Leonard. Penny meets Leonard's mom on their way through the lobby and on the way upstairs learns that she is a psychiatrist and neuroscientist. By the time they reach Leonard's apartment, Penny is in tears after being psychoanalysed. Sheldon, on the other hand, instantly develops a comfortable relationship with the elder Dr. Hofstadter, resulting in the two discussing 'intimate' relationship points, leading to a joint game of Rock Band. In the cafeteria at work, Howard thoroughly enjoys asking Leonard's mom about her other two, more successful children. Leonard gets his revenge by telling her that Howard lives with his mom and about Raj's selective mutism. She decides they are in an ersatz homosexual relationship. Later, Leonard and Penny seek comfort in each other and discuss Leonard's mother first over white wine, then tequila. As the night progresses, Leonard tells Penny that he built a hugging machine when he was ten so he could get physical affection (and that his dad used to borrow it). Penny increases the rules of their drinking games, resulting in a kiss. They eventually go to bed together, where at one point Leonard tells her what his mother's reasoning for their impending sex would be: psychologically, he is having sex with his mom and she with her dad. Needless to say, Penny immediately throws Leonard out.
33	16	"The Cushion Saturation"	Mark Cendrowski	Bill Prady & Lee Aronsohn (teleplay) Chuck Lorre (story)	March 2, 2009 (2009-03-02)	216
A paintball game leads to a romance for Wolowitz and Leslie (Sara Gilbert). At the apartment, Penny accidentally shoots the paintball gun at Sheldon's couch cushion (his "spot", his "only point of consistency in an ever-changing world"), and she and Leonard have a hard time getting it cleaned. They try just turning it over but Sheldon still notices the difference and turns it over to find the green stain. Penny has the cushion dry-cleaned, but it takes a week and Sheldon goes through withdrawal during that time. After Sheldon refuses to sit on the dry-cleaned cushion, Leonard reveals that the Szechuan Palace (the only place Sheldon has his cashew chicken from) closed 2 years ago and that he has been bringing home Chinese food from a different place and putting them in Szechuan Palace containers, of which he bought 4000 before the restaurant closed. Sheldon collapses onto the couch cushion but still doesn't like it. Meanwhile, Leslie and Howard start sleeping together at Howard's home, which lead to funny exchanges with Mrs. Wolowitz. Leslie is able to give Howard's work project some much-needed funds, although it turns out to be her way of controlling him. She asks him to come to her sister's wedding, he says no and she threatens to take away a trip to the CERN Large Hadron Collider project in Geneva. After getting over his initial reluctance to be in that sort of relationship, Howard accepts his "sex toy/arm candy" role. Sheldon finally gets his revenge by shooting Penny at the beginning of the group's next paintball game, which she decides to join. Penny then shoots Sheldon, who protests she's dead. Leonard agrees and shoots Sheldon himself, who promptly fires back. The others leave to surrender and then go to Denny's. The episode portrays all cast members playing paintball without face masks, presumably to aid their recognition (which is a major inaccuracy: paintball fields almost universally require eye protection to be worn at all times, due to the risk of severe eye injuries from stray projectiles.)
34	17	"The Terminator Decoupling"	Mark Cendrowski	Tim Doyle & Stephen Engel (teleplay) Bill Prady & Dave Goetsch (story)	March 9, 2009 (2009-03-09)	217
A train trip to a conference in San Francisco takes a major detour when Leonard, Sheldon, Wolowitz, and Raj discover that their favorite sci-fi actress, Summer Glau, is on board. But the fanboy frenzy quickly gives way to a heated mass debate when they realize one of them will have to approach her. They took the train because the vote was 3 to 1 for flying, with Sheldon the one vote for the train. While Wolowitz tries to think of a clever opening line for Summer, Raj starts talking to her after drinking what he later discovered was non-alcoholic beer. When he discovers this, of course, he quits talking. Wolowitz then takes over and creeps Summer out. Leonard eventually gets his chance, but Summer gets off the train before he can introduce himself. In a subplot, Sheldon needs Penny to find his flash drive so she can email him a paper he wants to show Nobel Prize laureate Dr. George Smoot (guest-starring as himself) in San Francisco. Leonard asks Sheldon why he can't just e-mail the paper when he returns, and Sheldon replies that he "wants to see [Smoot's] face light up when he reads it." Sheldon initially responds with hostility to Leonard's suggestion that Penny should retrieve the flash drive, reminding Leonard that "no one goes into my room". Sheldon relents, however, and spends most of the episode giving Penny meticulous instructions as to how to enter his room (of course, stipulating that he is granting her access for this one time only). The instructions lead to a Japanese puzzle box containing the flash drive. Sheldon attempts to give Penny instructions as how to open the box, but she instead puts it on the floor and smashes it open with her foot. After all of this effort, Smoot is not impressed with Sheldon's paper, asking him "With all due respect, Dr. Cooper, are you on crack?" When Sheldon initially calls Penny, she is talking to one of her friends about being in an upcoming play, which is her opportunity to portray Anne Frank. This is an in-joke referring to the fact that, when Kaley Cuoco was a cast member on 8 Simple Rules For Dating My Teenage Daughter, her character also played the role of Anne Frank in a high-school drama production.
35	18	"The Work Song Nanocluster"	Mark Cendrowski	Dave Goetsch & Richard Rosenstock (teleplay) Bill Prady & Lee Aronsohn (story)	March 16, 2009 (2009-03-16)	218
Penny has developed a home-made hair barrette called the "Pennyblossom," which has proven unexpectedly popular via word-of-mouth. She consults Sheldon for help in developing her product into a workable home business, which involves streamlining the creation process via assembly line and the episode's titular work songs. Leonard, Howard, and Raj add their own ideas for efficiency, production and marketing; Leonard, in particular, makes a sales website, with a one-day rush shipping option because "Amazon has one-day rush." Right away, they get an order for 1,000 Pennyblossoms from the "East Rutherford, New Jersey Gay/Lesbian/Bisexual/Transgender Alliance." The quintet work all night to finish, including the drastic measure of giving Sheldon caffeine, which, as they discover, turns him hyperactive and unproductive. The next morning, they discover that the same group has doubled their order, leading everyone to quit in exhaustion. All except Sheldon, who is now wide awake, in his Flash costume, and ready for more work (or at least a coffee run).
36	19	"The Dead Hooker Juxtaposition"	Mark Cendrowski	Steven Molaro	March 30, 2009 (2009-03-30)	219
The former tenants of unit 5A, the apartment above Leonard & Sheldon's, move out, replaced with an attractive woman named Alicia (Valerie Azlynn). Alicia, like Penny, is an actress, but a more successful one; by flirting with the guys, she manages to wrap Leonard, Wolowitz, and Raj around her finger; she even gains Sheldon's approval after an intense and bizarre interrogation in the building lobby. Penny attempts to re-assert primacy over her friends, bribing them with Chinese food, offering to watch Battlestar Galactica, and even memorizing a quantum physics joke, but Alicia still manages to snatch everyone away (but Sheldon) when she needs a quick ride to Universal Studios to audition for a role in CSI (specifically that of the episode's titular "Dead Hooker"). Alicia points out that Penny uses the same routine on the guys that Alicia does, and after that, the two have a catfight in the lobby, resulting in a black eye for Penny and ecstasy for Howard. At the end of the episode, Penny has reclaimed her men, while Alicia is with one of the producers of CSI and is heard "jumping up and down on the bed". This episode contains a number of callbacks to earlier moments in the series. Leonard and Sheldon's repeated-"hello" introductions to Alicia parallel their first meeting with Penny in the pilot episode. Sheldon, despite being oblivious to sarcasm in the earlier episodes of the series, attempts to employ it at Penny when she enters his apartment without asking his permission; likewise, Penny uses a Star Trek analogy when explaining the average physics nerd to Alicia. Finally, Penny and Sheldon reproduce an interrogation about Sheldon's peculiar chicken-with-broccoli tastes from The Griffin Equivalency, with Penny getting it (mostly) right where Leonard had failed.
37	20	"The Hofstadter Isotope"	Mark Cendrowski	David Goetsch	April 13, 2009 (2009-04-13)	220
While Stuart (Kevin Sussman), a fellow comic book-loving pal of the guys romances Penny, Leonard and Wolowitz venture out into the world of "Ladies' Night" at a local bar. Penny needs a comic book for her nephew's birthday, so she goes to the comic book store with the guys. Stuart, its owner, is also an artist. Leonard feels he and Stuart are basically the same person (i.e. the titular "isotope" of "Hofstadter"), so it pains him to see Penny with Stuart. He asks Wolowitz to "take me to a bar with women." However, Raj is the only one who succeeds in getting a girl, which baffles Wolowitz, who had been failing all night. Meanwhile, Sheldon interrupts Stuart's date with Penny to debate who should assume the identity of the Batman following the Batman R.I.P. storyline (Sheldon thinks Dick Grayson, Stuart Jason Todd); Sheldon "wins" the discussion when Stuart announces he is tired and wants to leave, whereupon they discover that Penny has fallen asleep from boredom.
38	21	"The Vegas Renormalization"	Mark Cendrowski	Steven Molaro (teleplay) Jessica Ambrosetti, Nicole Lorre & Andrew Roth (story)	April 27, 2009 (2009-04-27)	221
Leslie Winkle breaks up with Howard, and he becomes depressed. Leonard and Raj decide to take him on a trip to Las Vegas in order to cheer him up. While in Vegas, a prostitute named Mikaela (Jodi Lyn O'Keefe) begins talking to Raj. He and Leonard eventually decide to hire her to pose as a Jewish woman and seduce Howard. When Howard realizes what is going on, he thanks Leonard and Raj for setting up this "date." Sheldon, who has declined to come on the trip to Vegas, is ready to spend the weekend alone. He returns home to find that he has forgotten his key inside his locked apartment. Since the building manager will not arrive until the next morning, and Penny says she left her emergency key in their apartment, he is forced to spend the night with her. He sleeps in Penny's bed because he can't fit on the couch. When Leonard returns at the end of the episode, Sheldon comes out of Penny's apartment, telling Leonard he had dinner with her and spent the night. He also tells him that he has a better understanding of the term "friends with benefits," (which was a question he had the entire episode) before entering the apartment, leaving a bewildered Leonard looking shocked.
39	22	"The Classified Materials Turbulence"	Mark Cendrowski	Bill Prady & Steven Molaro (teleplay) Chuck Lorre & Lee Arohnson (story)	May 4, 2009 (2009-05-04)	222
The episode starts at the comic book store, where Howard is celebrating the launch of his "space toilet" (a special latrine for the ISS) by buying all of his friends new comics. Stuart tells Leonard he is having a second date with Penny and asks for advice. Leonard deliberately avoids Stuart's request, because he doesn't want Stuart to go further with Penny. Stuart visits the apartment for "last-minute advice" just before going to see Penny, but Leonard tells him to "go slow" with Penny, hoping that she will dump him. Leonard subsequently feels guilty about giving this advice, however, and goes to apologize to Stuart the next day. Stuart says that Leonard's advice was perfect - at first. He managed to get Penny drunk and started making out with her, but she accidentally blurted out Leonard's name. Leonard begins celebrating as soon as he's out of Stuart's sight. Howard, who was earlier celebrating the launch of his space toilet, discovers that he made a "teeny tiny error" that will cause the toilet to fail, dispensing its waste through the ISS (instead of out into space) after ten flushes. He asks Raj and Sheldon to help him construct a fix with materials that are readily available on the ISS. They eventually do throw together a fix. the episode's title is derived from the fact that Howard wished to keep his error as secret as possible, referring to it as "classified" when in front of both Penny and Stuart. The episode ends with all of the ISS astronauts asking to go on a spacewalk, presumably because their waste has leaked out of the toilet.
40	23	"The Monopolar Expedition"	Mark Cendrowski	Eric Kaplan & Richard Rosenstock	May 11, 2009 (2009-05-11)	223
Sheldon wins a National Science Foundation grant to pay for a three-month expedition to the North Magnetic Pole. His plan is to detect the magnetic monopoles in a way that would prove the validity of string theory. After some hesitation, he decides to go, and wants his three friends to join him. Howard is the most reluctant, as it means three months with Sheldon. Raj believes three months with Sheldon will earn him a better reincarnation life per his Hindu beliefs stating that three months with Sheldon means he will become a "well-hung billionaire... with wings". Leonard wants to go because he believes it will be a worthwhile experience. To prepare for the trip, the guys spend some time in the freezer at the Cheesecake Factory. When Penny learns about Leonard's trip, she is seemingly upset. She gives Leonard a Snuggie, or blanket with sleeves, as a gift saying she'll miss him and gives him a hug that Leonard feels lasts a long time. When, on the morning of his departure, Leonard asks Penny about what the long hug and the blanket mean, she tells him it only means she is going to miss him and wishes him a safe trip. However, after she closes the door, Penny whispers to herself "It means I wish you weren't going." Finally, the group departs to the Arctic, and there Wolowitz comically constructs a crossbow to shoot Sheldon but then remarks "There's no time for a crossbow; find me an icicle."

Season 3: 2009-10

The Big Bang Theory was renewed by CBS for a third season, which began airing on September 21, 2009. The number of episodes is as yet unknown. All the current main characters will return.

Series #	Season #	Title	Directed By	Written By	Original airdate	Prod. Code
41	1	"The Electric Can Opener Fluctuation"	Mark Cendrowski	Steven Molaro	September 21, 2009 (2009-09-21)	301
After their return home from their three-month expedition in the North Pole, Sheldon finds out from Howard and Raj that the guys had tampered with his experiment because Sheldon was absolutely unbearable when he wasn't getting the results he wanted (plans to kill him were even brought up and discussed). They tell him about their use of an electric can opener to give Sheldon positive results, thereby causing Sheldon to believe he has made a Nobel Prize-winning discovery. Unfortunately, Sheldon had immediately emailed everyone at Caltech about his discovery before Howard and Raj could tell him what had happened. Sheldon is so disgraced that he resigns and moves back in with his mother (played by Laurie Metcalf), who lives in east Texas. Mrs. Cooper calls Leonard and tells them that they should come talk to Sheldon. Upon the guys' arrival, Sheldon is intent on staying in Texas. However, he shortly has a disagreement with his mother about creationism versus evolution and decides to return home. Meanwhile, Penny has been harboring feelings for Leonard, which are released almost as soon as he comes home. Leonard's "moments" with her are constantly interrupted, and he "cannot catch a break." They finally sleep together at the end of the episode (Leonard finally "catches his break") and Leonard asks why it's always weird after friends sleep together and why they have to label it as such - "it just is what it is." Penny interrupts him saying "it's weird" and he replies "Totally."
42	2	"The Jiminy Conjecture"	Mark Cendrowski	Jim Reynolds	September 28, 2009 (2009-09-28)	302
Leonard and Penny struggle to recover from an awkward first hookup and try to figure how to overcome their current problem. A romantic evening between the pair soon turns to a night filled with drunken sickness. The next day Penny talks to Sheldon regarding her current problem with Leonard and Sheldon points out that if things don't work out, they can always return back to being friends. After Sheldon tells Leonard that he spoke to Penny about their problems, Leonard goes to Penny's apartment, there Penny tells Leonard that being friends was much simpler and that it will take the pressure off, something that Leonard agrees to. They decide to go back to being friends, however it's clear that neither wants that and soon give in to their attraction. Meanwhile, Sheldon and Howard stake their most valuable comic books (Sheldon's Flash against Howard's Fantastic Four) on a bet to determine the species of a cricket. Sheldon hears the chirps and says it is a snowy tree cricket and Howard insists it is a common field cricket. Along with Raj, the three spend a while locating the cricket. They settle the bet by taking "Toby" to Caltech's depressed entomologist, played by Lewis Black. Howard is correct that it is a common field cricket, so Sheldon has to give up his copy of The Flash. The title refers to the fact that Sheldon believed the name Jiminy (referencing Jiminy Cricket) to be a far more suitable name for a cricket than "Toby".
43	3	"The Gothowitz Deviation"	Mark Cendrowski	Lee Aronsohn & Richard Rosenstock (Story), Bill Prady & Maria Ferrari (Teleplay)	October 5, 2009 (2009-10-05)	303
After a sexual encounter that results in Penny's bed breaking, Penny and Leonard end up sleeping in Leonard's room, much to Sheldon's dismay. Penny then makes French Toast for breakfast, which does not meet Sheldon's weekly schedule (it's oatmeal day). During the episode, Sheldon tries to improve Penny using chocolate, rewarding her for what he considers to be correct behavior, as in operant conditioning with lab rats, despite Leonard's opposition. Howard and Raj go out to a goth club and meet two girls. After they say they would prefer to go "somewhere else and have some fun" the four end up in a tattoo shop, which makes Raj and Howard reveal their true selves and admit to not being goths, missing their opportunity with the girls rather than having tattoos. Leonard, Sheldon, and Penny are watching the anime Oshikuru: Demon Samurai, which is a reference to a 2004 episode of Two and a Half Men ("The Salmon Under My Sweater") in which Charlie and Jake collaborate on the theme song to the same show. Both series are created by Chuck Lorre.
44	4	"The Pirate Solution"	Mark Cendrowski	Steve Holland	October 12, 2009 (2009-10-12)	304
Raj must find a new job or be sent back to India. Sheldon has a solution, which is to allow Raj to work "for" him, rather than work "with" him. Raj reluctantly accepts the offer. With Raj working for Sheldon, it makes Howard lonely, so he tries to stay with Leonard and Penny (even making them breakfast) but they would rather be alone. Sheldon and Raj soon disagree on how to solve a work-related problem and Raj walks out. Sheldon actually apologizes at the end of the episode and he accepts that Raj was right but doesn't concede to him being wrong. The title refers to Sheldon's comment about Raj either immigrating to another country, returning to India, or "wandering the high seas as a stateless pirate."
45	5	"The Creepy Candy Coating Corollary"	Mark Cendrowski	Chuck Lorre & Bill Prady	October 19, 2009 (2009-10-19)	305
Sheldon enters a trading-card competition when he hears Wil Wheaton, for whom he harbors resentment, is also participating. Meanwhile, Wolowitz asks Penny to set him up with one of her friends.
46	6	"The Cornhusker Vortex"	Mark Cendrowski	Bill Prady & Steven Molaro	November 2, 2009 (2009-11-02)	306
Sheldon teaches Leonard how to understand football while a kite-fighting incident threatens Howard and Raj's friendship.

Weekly Ratings

U.S. standard ratings

In the following summary, "rating" is the percentage of all households with televisions that tuned to the show, and "share" is the percentage of all televisions in use at that time that are tuned in. "18-49" is the percentage of all adults aged 18–49 tuned into the show. "Viewers" is the number of viewers, in millions, watching at the time. "Rank" is how well the show did compared to other TV shows aired that week.

Season 1

The season's highest was episode 7 gathering a total of 9.68 million viewers.

Unless otherwise cited, the overnight rating, share, 18-49 and viewing information come from Your Entertainment Now. The weekly ranks come from The Programming Insider, unless otherwise referenced.

#	Episode	Air Date	Timeslot	Rating	Share	18-49	Viewers	Weekly Rank
1	"Pilot"	September 24, 2007	8:30 P.M.	6.0	9	3.7/9 (#3)	9.57 (#3)	#37
2	"The Big Bran Hypothesis"	October 1, 2007		5.5	8	3.4/8 (#2)	8.58 (#2)	#44
3	"The Fuzzy Boots Corollary"	October 8, 2007		5.3	8	3.4/8 (#2)	8.36 (#2)	#44
4	"The Luminous Fish Effect"	October 15, 2007		5.4	8	3.2/8 (#3)	8.15 (#4)	#49
5	"The Hamburger Postulate"	October 22, 2007		5.6	8	3.5/9 (#2)	8.72 (#2)	#44
6	"The Middle Earth Paradigm"	October 29, 2007		5.7	8	3.6/9 (#2)	8.92 (#2)	#45
7	"The Dumpling Paradox"	November 5, 2007		6.1	9	3.8/9 (#2)	9.68 (#2)	#38
8	"The Grasshopper Experiment"	November 12, 2007		5.9	9	3.8/9 (#2)	9.39 (#2)	#36
9	"The Cooper-Hofstadter Polarization"	March 17, 2008	8:00 P.M.	5.5	9	3.7/11 (#2)	9.11 (#2)	#23
10	"The Loobenfeld Decay"	March 24, 2008		5.3	9	3.4/10 (#2)	8.63 (#2)	#28
11	"The Pancake Batter Anomaly"	March 31, 2008		5.5	9	3.1/9 (#2)	8.68 (#2)	#33
12	"The Jerusalem Duality"	April 14, 2008		4.7	8	2.9/8 (#2)	7.69 (#3)	#34
13	"The Bat Jar Conjecture"	April 21, 2008		4.7	8	2.9/8 (#2)	7.51 (#4)	#42
14	"The Nerdvana Annihilation"	April 28, 2008		5.0	8	3.0/9 (#2)	8.16 (#4)	#34
15	"The Porkchop Indeterminacy"	May 5, 2008		4.7	8	2.8/9 (#2)	7.56 (#3)	#44
16	"The Peanut Reaction"	May 12, 2008		5.0	8	2.9/9 (#3)	7.88 (#3)	#38
17	"The Tangerine Factor"	May 19, 2008		4.7	8	2.7/8 (#3)	7.36 (#3)	#52

Season 2

Season 2 began airing on Monday, September 22, 2008 at 8:00 p.m.

On November 10, the show scored series-highs in total viewers in the 18-49 and 18-34 demographics, crossing the 10 million mark. On November 24, the show recorded series highs once again, this time against the Dancing with the Stars finale. On February 9, 2009, the show won its time slot in households while delivering its largest audience ever. The episode with the highest rating this season, so far, is episode 15, with a total of 13.11 million viewers.

#	Episode	Air Date	Timeslot	Rating	Share	18-49	Viewers	Weekly Rank
1	"The Bad Fish Paradigm"	September 22, 2008	8:00 P.M.	5.7	9	3.6/10 (#2)	9.36 (#2)	#34
2	"The Codpiece Topology"	September 29, 2008		5.4	8	3.3/9 (#2)	8.71 (#2)	#32
3	"The Barbarian Sublimation"	October 6, 2008		6.0	9	3.7/10 (#2)	9.32 (#2)	#26
4	"The Griffin Equivalency"	October 13, 2008		5.8	9	3.6/10 (#2)	9.36 (#2)	#23
5	"The Euclid Alternative"	October 20, 2008		5.8	9	3.5/9 (#2)	9.28 (#2)	#34
6	"The Cooper-Nowitzki Theorem"	November 3, 2008		5.9	9	3.7/10 (#1)	9.90 (#2)	#28
7	"The Panty Piñata Polarization"	November 10, 2008		6.2	9	3.9/10 (#1)	10.01 (#2)	#28
8	"The Lizard-Spock Expansion"	November 17, 2008		6.1	9	3.8/10 (#2)	9.76 (#2)	#33
9	"The White Asparagus Triangulation"	November 24, 2008		6.1	9	3.9/10 (#2)	10.03 (#2)	#24
10	"The Vartabedian Conundrum"	December 8, 2008		6.5	10	3.7/10 (#2)	10.80 (#2)	#18
11	"The Bath Item Gift Hypothesis"	December 15, 2008		6.8	11	4.2/11 (#1)	11.42 (#1)	#15
12	"The Killer Robot Instability"	January 12, 2009		7.2	11	4.4/11 (#1)	11.81 (#2)	#18
13	"The Friendship Algorithm"	January 19, 2009		6.5	10	4.0/10 (#2)	11.10 (#2)	#21
14	"The Financial Permeability"	February 2, 2009		6.7	10	4.1/10 (#2)	10.89 (#2)	#22
15	"The Maternal Capacitance"	February 9, 2009	9:30 P.M.	8.1	12	4.6/10 (#1)	13.11 (#1)	#15
16	"The Cushion Saturation"	March 2, 2009	8:00 P.M.	6.7	10	3.9/10 (#2)	10.94 (#2)	#21
17	"The Terminator Decoupling"	March 9, 2009		5.8	9	3.6/10 (#3)	9.46 (#3)	#31
18	"The Work Song Nanocluster"	March 16, 2009		5.9	9	3.7/11 (#3)	9.76 (#3)	TBA
19	"The Dead Hooker Juxtaposition"	March 30, 2009		6.0	11	3.8/11 (#2)	9.77 (#3)	TBA
20	"The Hofstadter Isotope"	April 13, 2009		6.1	10	3.8/11 (#3)	10.13 (#3)	TBA
21	"The Vegas Renormalization"	April 27, 2009		6.0	10	3.4/10 (#3)	9.31 (#3)	TBA
22	"The Classified Materials Turbulence"	May 4, 2009				3.4/10 (#3)	9.25 (#3)	TBA
23	"The Monopolar Expedition"	May 11, 2009		6.2	10	3.6/11 (#2)	9.81 (#3)	TBA

Season 3

#	Episode	Air Date	Timeslot	Rating	Share	18-49	Viewers	Weekly Rank
1	"The Electric Can Opener Fluctuation"	September 21, 2009	9:30 P.M.	TBA	TBA	4.7/10	12.96	#19
2	"The Jiminy Conjecture"	September 28, 2009		7.8	12	5.3/13	13.27	#16
3	"The Gothowitz Deviation"	October 5, 2009		7.7	11	4.7/11	12.52	#15
4	"The Pirate Solution"	October 12, 2009		7.9	12	4.8/12	12.8	TBA
5	"The Creepy Candy Coating Corollary"	October 19, 2009		N/A	N/A	N/A	N/A	TBA

External links

• CBS.com - official site
• Episodes Reviews in portuguese
• The Big Bang Theory Wiki
• Videos related to "The Big Bang Theory"