List of The Big Bang Theory episodes

The Big Bang Theory is an American comedy series created and executive produced by Chuck Lorre and Bill Prady. The pilot was directed by James Burrows.

The series is about two socially inept prodigies, Leonard (Johnny Galecki), and Sheldon (Jim Parsons), who are living across the hall from a beautiful girl with an average intellect, 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" 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 – 2008	September 2 2008	3	September 24, 2007	May 19, 2008	8.34	TBD	3.3/9 (TBA)
	2	22	2008 – 2009	TBA	TBA	September 22, 2008	Spring 2009	TBA	TBD	TBA

The first season of The Big Bang Theory ran for 17 episodes and originally aired between September 2007 and May 2008.

Season 1: 2007-2008

#	Title	Director	Writer(s)	Original airdate	Code
1	"Pilot"	James Burrows	Chuck Lorre & Bill Prady	September 24, 2007	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 their babies will be smart and beautiful), but Sheldon feels his friend is chasing a dream he'll never catch (adding 'and imaginary'). Sheldon is quite content spending 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 can not speak to attractive 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 and retrieve her TV from her ex boyfriend, Kurt's, place. However the boyfriend depants both Sheldon and Leonard and they are unable to retrieve the TV. Feeling bad Penny offers to buy them and their friends dinner.
2	"The Big Bran Hypothesis"	Mark Cendrowski	Robert Cohen & David Goetsch (teleplay); Chuck Lorre & Bill Prady (story)	October 1, 2007	102
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 Sheldon is obsessed. Penny wakes up and yells at them, prompting Leonard to ask how she knew (Sheldon had left an organizational diagram for her closet). Sheldon goes to apologize but Penny can not believe his attitude and remains upset. Later on Leonard goes to apologize, prompting Penny to hug him and say 'we're okay'.
3	"The Fuzzy Boots Corollary"	Mark Cendrowski	Steven Molaro & Bill Prady (teleplay); Chuck Lorre (story)	October 8, 2007	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 had seen was not her boyfriend, and 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 had suspected what he was up to.
4	"The Luminous Fish Effect"	Bob Koherr	David Litt & Lee Aronsohn (teleplay); Chuck Lorre & Bill Prady (story)	October 15, 2007	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 in 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 that 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..."
5	"The Hamburger Postulate"	Andrew D. Weyman	Steven Molaro & David Goetsch (teleplay); Jennifer Glickman (story)	October 22, 2007	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. 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.
6	"The Middle-Earth Paradigm"	Mark Cendrowski	Robert Cohen & David Litt (teleplay); David Goetsch (story)	October 29, 2007	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 more 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. 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 a to be 'good listener' (as Koothrappali is so shy he can not speak to attractive women).
7	"The Dumpling Paradox"	Mark Cendrowski	Lee Aronsohn & Jennifer Glickman (teleplay); Bill Prady & Chuck Lorre (story)	November 5, 2007	107
Penny's slutty '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 instead go dancing with her friend. Believing 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.
8	"The Grasshopper Experiment"	Ted Wass	Robert Cohen & Lee Aronsohn (teleplay); David Goetsch & Steven Molaro (story)	November 12, 2007	108
Koothrappali is overwhelmed after his parents arrange a blind date with a girl from his childhood, as he can not 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 fairytale princess. Koothrappali and Leonard return to Leonard's apartment where Koothrappli 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").
9	"The Cooper-Hofstadter Polarization"	Joel Murray	David Goetsch & Chuck Lorre & Lee Aronsohn (teleplay); Bill Prady & Stephen Engel (story)	March 17, 2008	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 has a physical altercation with Leonard. In the end, the fight is captured by Wolowitz and put on Youtube.
10	"The Loobenfeld Decay"	Mark Cendrowski	Bill Prady & Lee Aronsohn (teleplay); Chuck Lorre (story)	March 24, 2008	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 wont hurt her feelings. Sheldon becomes paranoid that Leonard's lie was 'too transparent' and eventually creates an intricate lie about his non-existent drug addicted cousin Leo (DJ Qualls), 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 physcist (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, thus the lie did him no good at all.
11	"The Pancake Batter Anomaly"	Mark Cendrowski	Bill Prady & Stephen Engel (teleplay); Lee Aronsohn & Chuck Lorre (story)	March 31, 2008	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. 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."
12	"The Jerusalem Duality"	Mark Cendrowski	Steven Molaro & David Goetsch (teleplay); Stephen Engel & Jennifer Glickman (story)	April 14, 2008	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 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 'human 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 yet they were not.
13	"The Bat Jar Conjecture"	Mark Cendrowski	Bill Prady & Robert Cohen (teleplay); Stephen Engel & Jennifer Glickman (story)	April 21, 2008	113
The guys decided to compete in a physics bowl but 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 anymore". 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. After being told it is to defeat Sheldon she joins as Sheldon had once told her that she should give up her research to bear children and do laundry. 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 the janitor's answer be accepted...even though it was correct (in America he's a janitor, but in the former Soviet Union he had been 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 are able to properly answer any of the questions.
14	"The Nerdvana Annihilation"	Mark Cendrowski	Stephen Engel & Steven Molaro (teleplay); Bill Prady (story)	April 28, 2008	114
The episode is sometimes called The Nerdmabelia Scattering. Leonard buys a replica time machine online 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 'nerdmabelia' and the guys try to convince him not to (or sell it to them, whichever). In the end Sheldon confronts Penny about her own love of childish things (Hello Kitty, Beanie Babies, 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.
15	"The Shiksa Indeterminacy"	Mark Cendrowski	Bill Prady & Lee Aronsohn (teleplay); Chuck Lorre (story)	May 5, 2008	115
The guys see an attractive woman in Sheldon's office and can not 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 her 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 her 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'.
16	"The Peanut Reaction"	Mark Cendrowski	David Goetsch & Steven Molaro (teleplay); Lee Aronsohn & Bill Prady (story)	May 12, 2008	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 pretending 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.
17	"The Tangerine Factor"	Mark Cendrowski	Chuck Lorre & Bill Prady & Steven Molaro & Lee Aronsohn	May 19, 2008	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 'Orange Chicken' as 'Tangerine Chicken'...a lesser citrus. He doesn't become very good at it, and as a result the owner (James Hong) thinks he's crazy due to his hilarious mistranslations ("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.

Season 2: 2008-2009

#	Title	Director	Writer(s)	Original airdate	Code
18	"The Bad Fish Paradigm"	Mark Cendrowski	Bill Prady & Steven Molaro & David Goetsch	September 22, 2008	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. They try to convince Leonard that the date wasn't working well: they think that when Penny said "let us slow down a bit", it meant that the "fish is bad". But they are obviously envious. On the other hand, after Penny and Leonard's date, Penny feels uncomfortable having not gone to 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 facial expressions) and results in a drastic decision on Sheldon's part.
19	"The Codpiece Topology"	Mark Cendrowski	Chuck Lorre & Bill Prady & Lee Aronsohn	September 29, 2008	202
The guys return from a Renaissance Fair 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 who convinces Sheldon to leave the apartment, to give his roommate and Leslie some privacy. On the staircase, while playing Super Mario 64, 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 Leonard. After which Sheldon tells Leonard to look on the bright side Leonard then replies with "What's the bright side?" Sheldon states that it is only 9 more months to Comic-Con. (In this episode it is revealed that at Comic-Con Raj made out with an attractive man dressed as a Green Orion Slave Girl.)
20	"The Barbarian Sublimation"	Mark Cendrowski	Nicole Lorre & Steve Molaro & Eric Kaplan	October 6, 2008	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 realizes what she's done and promptly stops playing the game.
21	"The Griffin Equivalency"	Mark Cendrowski	Chuck Lorre & Bill Prady & Stephen Engel & Tim Doyle	October 13, 2008	204
Raj gets an ego boost after winning some fame from a magazine article and risks his friendship with Leonard by trying to win over Penny.
22	"The Euclid Alternative"	TBA	TBA	October 20, 2008	205
TBA

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