The Big Bang Theory (season 2)

Second season DVD cover art
Country of origin	United States
No. of episodes	23
Release
Original network	CBS
Original release	September 22, 2008 (2008-09-22) – May 11, 2009 (2009-05-11)

The second season of the American sitcom The Big Bang Theory was originally aired on CBS from September 22, 2008, to May 11, 2009, over 23 episodes. The Complete Season DVD was released September 15, 2009, and a Blu-ray version was reissued on July 10, 2012, with remastered surround sound audio, whereas the DVD version only had stereo. Season two starts immediately after the end of season one with Leonard and Penny's date.

Cast

Main article: List of The Big Bang Theory characters

• Dr. Leonard Hofstadter, portrayed by Johnny Galecki, is an experimental physicist with an IQ of 173 who received his doctorate when he was 24 years old. He shares an apartment with colleague and friend Sheldon Cooper and is the straight man of the series. He and Penny dated once at the beginning of the season.
• Dr. Sheldon Cooper, portrayed by Jim Parsons, is a theoretical physicist. Originally from East Texas, he was a child prodigy, starting college at the age of 11, right after completing the fifth grade. He has an IQ of 187 and exhibits a strict adherence to routine; a lack of understanding of irony, sarcasm and humor; and a complete lack of humility. Leonard describes Sheldon as being "one lab accident away from being a super-villain".
• Penny, portrayed by Kaley Cuoco, is a waitress who lives across the hall from Leonard and Sheldon. She has aspirations of a career in show business, and has been to casting calls and auditions but has not been successful thus far. Her last name has never been revealed.
• Howard Wolowitz, portrayed by Simon Helberg, works as an aerospace engineer. He is Jewish, and lives with his mother. Unlike Sheldon, Leonard, and Raj, Howard lacks a Ph.D. He defends this by pointing out that he has a master's degree in Engineering from MIT and the apparatus he designs are actually built and launched into space, unlike the purely abstract work of his friends. He provides outrageous pick-up lines and fancies himself a ladies man with suitably unimpressed reactions from Penny and has limited success with other women.
• Dr. Rajesh "Raj" Koothrappali, portrayed by Kunal Nayyar, originally comes from New Delhi, India. Known commonly as "Raj", he works as an astrophysicist at Caltech. He is very shy around women and is unable to talk to them unless he drinks alcohol. However, he has much better luck with women as opposed to his overly confident best friend Howard.
• Leslie Winkle, portrayed by Sara Gilbert, is an experimental physicist who has casual sex with both Howard and Leonard during the show's airing. She does not get along well with Sheldon and frequently mocks him.

Episodes

See also: List of The Big Bang Theory episodes

Season two begins to deal with character development, including Sheldon becoming more and more obsessive. 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, managing to start a short-lived sexual relationship with Leslie Winkle in the second half of the season. Meanwhile, Rajesh manages to briefly apologize to Penny for what he did in "The Griffin Equivalency" without having consumed alcohol.

Season 2 episodes

No. overall	No. in season	Title	Directed by	Written by	Original air date	Prod. code	U.S. viewers (millions)
18	1	"The Bad Fish Paradigm"	Mark Cendrowski	Story by: Bill Prady Teleplay by: Dave Goetsch & Steven Molaro	September 22, 2008 (2008-09-22)	3T7351	9.36
Continued from the Season 1 finale, Leonard and Penny return from their first date while Howard and Raj spy on them using a webcam. Leonard, spotting the camera, suggests going over to Penny's apartment, but she misunderstands him and tells him to "slow things down". The guys try to convince Leonard that the date did not go too well, which he denies. Penny later tells Sheldon that she lied to Leonard about graduating from community college, feeling Leonard would not want to date a woman who is not smart, and makes him promise not to tell him. Sheldon finds it difficult to keep the secret and moves out of the apartment as a result. He first stays in Raj's apartment, but after he criticizes Aishwarya Rai (comparing her to Madhuri Dixit), Raj leaves him with Howard. At Howard's house, Sheldon is unable to sleep, so Howard gives him Valium and takes him back to the apartment. Sheldon, in his drugged state, tells Leonard the secret. The next morning, Leonard suggests Penny should join Pasadena City College, but tells her that he does not mind dating someone who is not smart after she asks, to which she slams her door in his face. Recurring character: Carol Ann Susi as Mrs. Wolowitz Note: The title sequence was updated with this episode. Title reference: Howard calling Leonard a "bad fish" in his relationship with Penny.
19	2	"The Codpiece Topology"	Mark Cendrowski	Story by: Chuck Lorre Teleplay by: Bill Prady & Lee Aronsohn	September 29, 2008 (2008-09-29)	3T7352	8.76
After the guys return from a Renaissance fair and see Penny with her new boyfriend, Eric, Leonard decides to once again pursue a relationship with Leslie. Leslie agrees to date Leonard, assuming the dominant role before conceding that Leonard should assume the "male role". With this new attitude, Leslie goes as far as evaluating Leonard's genetic defects, and talking about procreating with him. Penny dumps Eric after unsuccessfully using him to make Leonard jealous. Sheldon explains to Penny that he feels uncomfortable with Leonard dating his arch enemy, Leslie, but approves the relationship after Penny's advice. However, almost immediately, Leslie and Sheldon argue over the validity of loop quantum gravity, which Leslie supports, and string theory, which Sheldon supports. Leslie expects Leonard to back up her beliefs, but when Leonard backs up Sheldon, Leslie dumps him, much to Sheldon's relief. Recurring character: Sara Gilbert as Leslie Winkle Guest star: Travis Schuldt as Eric Title reference: Sheldon stating that the Renaissance Fair was just an excuse to wear a codpiece.
20	3	"The Barbarian Sublimation"	Mark Cendrowski	Story by: Nicole Lorre Teleplay by: Steven Molaro & Eric Kaplan	October 6, 2008 (2008-10-06)	3T7353	9.33
Sheldon lets Penny into his apartment after she accidentally locks herself out. Penny, frustrated by not progressing in her acting career and not having sex for six months, becomes curious when seeing Sheldon play Age of Conan. Penny quickly becomes addicted and experiences video game addiction. After talking with Leslie, Sheldon realizes that Penny needs to have sex to relieve her stress and regain her regular life. Sheldon attempts to set Penny up with an online dating service, but fails. In the end, Penny overcomes her addiction when she realizes she accepted to have a virtual date with Howard. Horrified, she promptly stops playing. Recurring characters: Sara Gilbert as Leslie Winkle and Mark Harelik as Dr. Eric Gablehauser Title reference: Penny becoming addicted to playing the computer game Age of Conan set in Robert E. Howard's universe of Conan the Barbarian.
21	4	"The Griffin Equivalency"	Mark Cendrowski	Story by: Bill Prady & Chuck Lorre Teleplay by: Stephen Engel & Tim Doyle	October 13, 2008 (2008-10-13)	3T7354	9.36
Raj is included in People magazine's "30 Visionaries Under 30 Years Old to Watch" list for his discovery of the trans-Neptunian object 2008 NQ17, sparking jealousy from his friends. Despite Leonard's comments that they need to be supportive, Raj becomes arrogant after receiving star treatment from Dr. Gablehauser and getting an assistant, so the guys ditch him. Raj invites Penny to People's reception. After the party, a very intoxicated Raj returns home with Penny, and via webcam introduces her to his parents as his girlfriend. The night ends with Penny denying being Raj's girlfriend, and leaving after he becomes sick from over drinking. The following morning, a sober and shy Raj tries to apologize to Penny, attempting to leave a written note, but Penny forces him to utter a barely audible "sorry" before forgiving him. Recurring character: Mark Harelik as Dr. Eric Gablehauser, Brian George as Dr. V.M. Koothrappali and Alice Amter as Mrs. Koothrappali Note: Cameo appearance by Charlie Sheen Title reference: Sheldon wishing a griffin as his ideal pet and considering a substitute for Raj as a friend.
22	5	"The Euclid Alternative"	Mark Cendrowski	Story by: Bill Prady & Steven Molaro Teleplay by: Lee Aronsohn & Dave Goetsch	October 20, 2008 (2008-10-20)	3T7355	9.28
Leonard is working on an experiment for several days, resulting in his inability to drive Sheldon to the university. Sheldon asks Penny, Howard and Raj for assistance, but they all eject him from their vehicles for being annoying. The group finally stage an "intervention" and tell Sheldon to get a driver's license and learn to drive. After a trip to the DMV, resulting in Sheldon getting his learner's permit, the group set up a driving simulator for him in the living room. Sheldon does horribly as a driver, so he decides to live in his office at the university so that he does not have to commute. However, Leonard reveals that he actually finished his experiment a week ago and just wanted to avoid driving Sheldon to work. Guest star: Octavia Spencer as DMV employee Title reference: The Euclid Avenue that Sheldon is afraid of passing through on his way to work.
23	6	"The Cooper–Nowitzki Theorem"	Mark Cendrowski	Story by: Stephen Engel & Daley Haggar Teleplay by: Tim Doyle & Richard Rosenstock	November 3, 2008 (2008-11-03)	3T7356	9.67
After a lecture by Leonard and Sheldon, a graduate student named Ramona Nowitzki becomes obsessed with Sheldon and insinuates herself into his life as a platonic girlfriend/assistant. Ramona proves to be a helpful influence on Sheldon's work, but she annoys him by prohibiting his recreational activities and forcing him to solely concentrate on his research. Eventually Sheldon realizes that he is in "some sort of relationship" with Ramona, and seeks help from Penny and Leonard to get rid of her, without success. Sheldon eventually reaches a breakthrough in his research and, grateful to Ramona, asks if he can do something for her. Ramona suggests they share credit for his discovery calling it "The Cooper-Nowitzki Theorem", but Sheldon refuses and kicks Ramona out. After reading a draft paper of the new theorem, another student approaches Sheldon in the same way Ramona did the first time. Recurring character: Sara Gilbert as Leslie Winkle Guest star: Riki Lindhome as Ramona Nowitzki Title reference: Ramona Nowitzki's suggested name for the theorem that Sheldon develops.
24	7	"The Panty Piñata Polarization"	Mark Cendrowski	Story by: Bill Prady & Tim Doyle Teleplay by: Jennifer Glickman & Steven Molaro	November 10, 2008 (2008-11-10)	3T7357	10.01
When Penny's cable gets cut, she comes over to the guys' apartment to watch America's Next Top Model. However, she accidentally sits on Sheldon's spot on the couch and touches his onion rings, prompting Sheldon to banish her from his apartment. Sheldon and Penny then aim to one-up the other, with Sheldon cutting Penny's Wi-fi and Penny ruining Sheldon's laundry night. Eventually, after Sheldon places Penny's laundry on a telephone wire, Leonard tells Penny to complain to Sheldon's mother. Sheldon's mother forces Sheldon to apologize to Penny and give back her laundry. Meanwhile, Howard finds out that the models in America's Next Top Model are in a house in Los Angeles. Determined to get in the house, he and Raj search the house using all available technology and successfully find it. Howard and Raj end up entering the house by posing as cable guys. Guest stars: Analeigh Tipton as herself and Samantha Potter as herself Title reference: Sheldon hanging Penny's laundry from a wire and taunting her to play Panty Piñata.
25	8	"The Lizard–Spock Expansion"	Mark Cendrowski	Story by: Bill Prady Teleplay by: Dave Goetsch & Jennifer Glickman	November 17, 2008 (2008-11-17)	3T7358	9.76
Howard meets Dr. Stephanie Barnett at a bar and invites her to drive the Mars rover at the Jet Propulsion Laboratory, but the plan fails when the rover gets stuck in a Martian ditch. Howard subsequently destroys all security tapes and hard drives relating to the mission. Afterwards, Leonard admits to Howard that he has started dating Stephanie, but Howard forgives him when Stephanie sets up him with another friend, and invites him on a double-date. In the end, Howard hears the news on TV that the rover found water on Mars in the bottom of the ditch, but as the data was destroyed, no one was able to determine who was responsible for the discovery. Meanwhile, Sheldon and Raj play a game of rock-paper-scissors-lizard-Spock, a "The Lizard-Spock Expansion" of the traditional game rock-paper-scissors. They play to decide who gets to watch what on TV, but they both choose Spock. They, along with Howard, play the game for the last dumpling. When they choose all Spock again, they play it where none of them may hold up Spock, but they all choose Spock again anyway. Recurring characters: Sara Rue as Dr. Stephanie Barnett and Carol Ann Susi as Mrs. Wolowitz Title reference: Sheldon's proposal to use the game "Rock-paper-scissors-lizard-Spock", an expanded form of the game "Rock-paper-scissors".
26	9	"The White Asparagus Triangulation"	Mark Cendrowski	Story by: Dave Goetsch & Steven Molaro Teleplay by: Stephen Engel & Richard Rosenstock	November 24, 2008 (2008-11-24)	3T7359	10.19
Sheldon considers Stephanie the only "tolerable" girlfriend that Leonard has had, and tries helping Leonard in the relationship as a result, fearing Leonard will ruin it. However, Sheldon irritates Leonard by joining the couple when they have a romantic dinner and go to the movies. After believing that Leonard is losing Stephanie, 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. Following the trip to the hospital, Leonard finds Sheldon hacked his Facebook account and changed his status to "In a relationship". Leonard worries that this will make him look desperate, but then finds that Stephanie changed her status to "Stephanie Barnett is in a relationship with Leonard Hofstadter". Sheldon then proclaims "Dr. Sheldon Cooper for the win." Recurring character: Sara Rue as Dr. Stephanie Barnett Title reference: The content of the jar that Leonard breaks, and the relationship triangle (Leonard-Stephanie-Sheldon) that features prominently.
27	10	"The Vartabedian Conundrum"	Mark Cendrowski	Story by: Chuck Lorre & Steven Molaro Teleplay by: Bill Prady & Richard Rosenstock	December 8, 2008 (2008-12-08)	3T7360	10.80
Stephanie moves into Leonard and Sheldon's apartment for practical purposes, though Leonard does not acknowledge this. Stephanie gives a physical examination to Sheldon, who complains about a ringing in his ear, but after Penny, unaware of the relationship, shows up in the guys' apartment, she attempts to prove to Leonard that Stephanie is living with him. After Stephanie buys Leonard new clothes that he ends up hating, Leonard realizes that his relationship with Stephanie is moving too fast for him. Leonard tries to tell Stephanie to move out, but every time he tries, she diverts him by initiating sex. Meanwhile, Sheldon sneaks into the hospital to test himself, as the ringing has not stopped. By the time Leonard gets back to the apartment, Stephanie has diagnosed Sheldon with a fake larynx inflammation, and instructs him not to speak at all. She calls the diagnosis a "Sheldonectomy". Recurring character: Sara Rue as Dr. Stephanie Barnett Title reference: Sheldon cannot understand why the third-floor neighbor, Mrs. Vartabedian, dislikes him.
28	11	"The Bath Item Gift Hypothesis"	Mark Cendrowski	Story by: Bill Prady & Richard Rosenstock Teleplay by: Stephen Engel & Eric Kaplan	December 15, 2008 (2008-12-15)	3T7361	11.42
Sheldon worries about the approaching Christmas holidays and his indecision about what to buy for Penny. After deciding on a basket of bath items, he discovers a wide selection available, but unsure about what Penny is going to get him, he buys an entire array to cover all contingencies. Penny's gift to Sheldon is a napkin both autographed and used by Leonard Nimoy. Sheldon, overwhelmed since he now possesses Nimoy's DNA and can grow his own Leonard Nimoy, gives Penny all of the gift baskets and then a rare "Sheldon" hug. Meanwhile, Leonard meets visiting researcher and fellow experimental physicist Dr. David Underhill. Although Leonard envies David for being handsome and a more successful physicist than himself, he still jumps at David's offer to help him in his research. However, things come to a halt when David meets Penny and the two start dating. They later break up after Penny finds out he is married. Guest star: Michael Trucco as Dr. David Underhill Note: Jim Parsons submitted this episode for consideration due to his nomination for the Primetime Emmy Award for Outstanding Lead Actor in a Comedy Series at the 61st Primetime Emmy Awards. Title reference: The gift that Sheldon gives to Penny.
29	12	"The Killer Robot Instability"	Mark Cendrowski	Story by: Bill Prady & Richard Rosenstock Teleplay by: Steven Molaro & Daley Haggar	January 12, 2009 (2009-01-12)	3T7362	11.81
Howard designs a robot, M.O.N.T.E. (Mobile Omnidirectional Neutralization and Termination Eradicator) for the "Southern California Robot Fighting League Round Robin Invitational", which the guys plan to enter. When Penny arrives at the apartment, Howard begins to flirt with her, but pushes her too far and causes her to furiously lash out at him. Depressed, Howard returns home and remains in his room, refusing to go to work. Leonard advises Penny to go to Howard's house and apologize. Howard tells Penny about all his failed romances, and Penny consoles him by saying that he is a good guy at heart and he just tries too hard to get girls. After this however, Howard tries to kiss Penny, which results in her punching him. Howard is left happy, feeling he is halfway to 'pity sex'. Meanwhile, the guys' co-worker Barry Kripke also enters the competition and challenges Sheldon and the guys to a one-on-one fight using their robots. Sheldon accepts, but Kripke's robot turns out to be far superior to M.O.N.T.E. and, with Howard indisposed, Barry easily wins. Sheldon refuses to throw the towel in, resulting in M.O.N.T.E. being destroyed by Kripke's robot. Recurring characters: John Ross Bowie as Barry Kripke and Carol Ann Susi as Mrs. Wolowitz Title reference: The killer robot created by the guys.
30	13	"The Friendship Algorithm"	Mark Cendrowski	Story by: Bill Prady & Richard Rosenstock Teleplay by: Chuck Lorre & Steven Molaro	January 19, 2009 (2009-01-19)	3T7363	11.10
Sheldon hears that Kripke is in control of an Open Science Grid computer, so he plans to befriend him to gain access to it. Socially inept, Sheldon struggles, and his current friends prove not of much help in the same respect. During a trip to the bookstore, Sheldon tries making friends with a little girl, but Leonard gets him to quickly exit before he is picked up as a pedophile. Sheldon uses a children's book to help him design a flowchart to get new friends. This pays off as Sheldon goes rock-climbing with Kripke, but Sheldon faints due to his fear of heights. Back at the apartment, Sheldon decides to cut off Raj as a friend to make room for Kripke. However, when Kripke reveals he does not actually control the computer, Sheldon dismisses him and restores Raj as a friend. Recurring character: John Ross Bowie as Barry Kripke Title reference: The algorithm created by Sheldon that he uses to make friends with Kripke.
31	14	"The Financial Permeability"	Mark Cendrowski	Story by: Chuck Lorre & Steven Molaro Teleplay by: Richard Rosenstock & Eric Kaplan	February 2, 2009 (2009-02-02)	3T7364	10.89
Penny is experiencing financial difficulties, which may result in her finding a new place to live. Sheldon, after discussing it with her, does the logical thing and lends her some money. After Leonard learns about Penny's problems, he tries to help her cut expenses, and in the process learns that her ex-boyfriend Kurt owes her $1,800. Without telling Penny, Leonard and the guys go to Kurt's place to collect the money. Though they are unsuccessful, Kurt writes "I owe Penny $1800, Kurt" on Leonard's forehead in indelible ink. Penny later pays Sheldon back after Kurt pays her back, but, much to Leonard's disappointment, Kurt never told Penny about Leonard's visit, and instead took the opportunity to get back together with her. Recurring character: Brian Patrick Wade as Kurt Title reference: Sheldon shows he is very willing to help his friends financially when he offers to help Penny.
32	15	"The Maternal Capacitance"	Mark Cendrowski	Story by: Chuck Lorre & Bill Prady Teleplay by: Richard Rosenstock & Steven Molaro	February 9, 2009 (2009-02-09)	3T7365	13.11
Leonard becomes worried when he learns his mother, accomplished psychiatrist and neuroscientist Dr. Beverly Hofstadter, is coming to visit. Upon arriving, Beverly meets Penny, and by the time they reach Leonard's apartment, Penny is in tears after having her childhood issues psychoanalyzed. Sheldon, on the other hand, instantly develops a comfortable relationship with Leonard's mother, who turns out to be as strict and logical as himself. Howard and Raj also meet Beverly, but after learning that Howard still lives with his mother and Raj cannot talk to women, she is quick to declare that they are in an "ersatz homosexual marriage". Leonard later goes to talk to Penny and they comfort each other by discussing their respective childhood issues with their parents. As they become drunk, Penny and Leonard are about to have sex, but Leonard ruins the moment by using psychology and noting that he is having sex with his mom and she with her dad. Disgusted, Penny throws Leonard out of her apartment. Recurring character: Christine Baranski as Dr. Beverly Hofstadter Note: This was the most watched episode of season 2, with 13.11 million viewers. Christine Baranski submitted this episode for consideration due to her nomination for the Primetime Emmy Award for Outstanding Guest Actress in a Comedy Series at the 61st Primetime Emmy Awards. Title reference: Leonard's mother visiting him.
33	16	"The Cushion Saturation"	Mark Cendrowski	Story by: Chuck Lorre Teleplay by: Bill Prady & Lee Aronsohn	March 2, 2009 (2009-03-02)	3T7366	10.94
After a paintball match, Penny accidentally shoots a paintball gun at Sheldon's couch cushion, and she and Leonard have a hard time getting it cleaned. Sheldon, upset and still dissatisfied with dry-cleaning, team-kills Penny in the next paintball game, causing the others to surrender. Meanwhile, Leslie and Howard begin a relationship after sleeping together during the match. Leslie secure funds for his work and even invites him to a trip to the CERN Large Hadron Collider project in Geneva. However, this turns out to be just Leslie's way to control Howard. Although initially reluctant, Howard later happily accepts his role as a "sex toy/arm candy". Recurring character: Sara Gilbert as Leslie Winkle Title reference: Sheldon's cushion, which Penny "saturates" with paint.
34	17	"The Terminator Decoupling"	Mark Cendrowski	Story by: Bill Prady & Dave Goetsch Teleplay by: Tim Doyle & Stephen Engel	March 9, 2009 (2009-03-09)	3T7367	9.46
The guys take a trip to a conference in San Francisco to meet guest speaker and 2006 Nobel Prize laureate Dr. George Smoot. On the train, the guys realize Summer Glau of Terminator: The Sarah Connor Chronicles is on board. Raj is the first to approach Summer, and she gets along with him, but Raj notices that he drank non-alcoholic beer before approaching her, causing a placebo effect and Raj to revert to his usual timid self. Howard then takes over, but creeps Summer out with his awkward style. Leonard finally gets his chance, but Summer gets off the train before he can introduce himself. Meanwhile, Sheldon realizes he forgot his USB flash drive with a paper he wants to show to Smoot, and needs Penny's help to find it and email it to him. However, Smoot is not impressed, asking him "With all due respect, Dr. Cooper, are you on crack?" Guest stars: Summer Glau as herself and George Smoot as himself Title reference: Summer Glau and George Smoot's guest-starring on the show.
35	18	"The Work Song Nanocluster"	Peter Chakos	Story by: Bill Prady & Lee Aronsohn Teleplay by: Dave Goetsch & Richard Rosenstock	March 16, 2009 (2009-03-16)	3T7368	9.76
Penny develops home-made hair barrettes called 'Penny Blossoms' and aims to turn them into a profitable homebased business. With Sheldon's help, Penny develops an efficient assembly line before Leonard, Howard, and Raj join in. Leonard designs the sales website, and they immediately get an order for a thousand Penny Blossoms from the East Rutherford, New Jersey Gay-Lesbian-Bisexual-Transgender Alliance. Despite their initial happiness, they realize Leonard included a one-day rush shipping option on the website, so the group has to work all night to fulfill the order. However, the next morning, they discover that the same group doubled their order, leading the guys to quit in exhaustion. Sheldon, drinking coffee to stay awake, races around the apartment dressed as The Flash. Title reference: A song that Sheldon and Penny sing to improve the manufacturing process.
36	19	"The Dead Hooker Juxtaposition"	Mark Cendrowski	Steven Molaro	March 30, 2009 (2009-03-30)	3T7369	9.77
The former tenants of the apartment above Leonard and Sheldon's move out. After an unsuccessful attempt by Howard to rent the apartment, an attractive blonde woman named Alicia moves in. Alicia, like Penny, is an aspiring actress who obtains a role as a dead hooker in an episode of the TV series CSI. The guys become fascinated with Alicia, and she takes advantage by having them labor for her. As a result, Penny loses the guys' attention, and also comes to resent the way Alicia exploits them. Penny tries to win her friends back by bribing them with Chinese food, offering to watch Battlestar Galactica, and even memorizing a quantum physics joke. After Alicia brags about her exploitation of the men, while also expressing derision of their incomes, Penny confronts her. Alicia responds by saying that Penny exploits the men in the same way that she herself does, causing Penny to attack her. After the fight, the guys learn that Alicia is sleeping with one of the CSI producers, leading Penny to comment that Alicia is a "dead whore on TV, live one in real life". Recurring character: Carol Ann Susi as Mrs. Wolowitz Guest star: Valerie Azlynn as Alicia Title reference: Penny's line summarizing Alicia's behavior as sleeping her way to success as an actress while playing a dead prostitute in the television show CSI.
37	20	"The Hofstadter Isotope"	Mark Cendrowski	Dave Goetsch	April 13, 2009 (2009-04-13)	3T7370	10.13
When Penny accompanies the guys to the comic book store to buy a present for her nephew's birthday, the owner, Stuart, asks her out on a date, prompting jealousy from Leonard. To take his mind off the situation, Leonard asks Howard and Raj to take him to a bar to socialize with women, but neither he nor Howard succeed in finding a woman. Stuart's date with Penny goes well, but they are interrupted by Sheldon, who starts an argument with Stuart about who Bruce Wayne's successor as Batman should be, during which Penny falls asleep. Recurring character: Kevin Sussman as Stuart Bloom Note: This episode marks the first appearance of future regular cast member Kevin Sussman as Stuart Bloom. Title reference: Leonard claims that Stuart is essentially the same person as he is.
38	21	"The Vegas Renormalization"	Mark Cendrowski	Story by: Jessica Ambrosetti, Nicole Lorre & Andrew Roth Teleplay by: Steven Molaro	April 27, 2009 (2009-04-27)	3T7371	9.31
Leslie ends her "friends with benefits" relationship with Howard, upsetting him. Leonard and Raj decide to take him on a trip to Las Vegas, Nevada to cheer him up. There, a prostitute named Mikayla approaches Raj, and he and Leonard decide to hire her for Howard. Howard soon realizes she is a prostitute, but nevertheless thanks Leonard and Raj for setting up the "date". Meanwhile, Sheldon, who has declined to go to Las Vegas, is delighted to spend the weekend alone, until he forgets his apartment key. He is forced to spend the night at Penny's apartment, and, in the process, thinks he has a better understanding of the term "friends with benefits". Guest star: Jodi Lyn O'Keefe as Mikayla Title reference: The trip to Las Vegas that brought Howard back to his old ways.
39	22	"The Classified Materials Turbulence"	Mark Cendrowski	Story by: Chuck Lorre & Lee Aronsohn Teleplay by: Bill Prady & Steven Molaro	May 4, 2009 (2009-05-04)	3T7373	9.25
Howard celebrates the launch of his latest invention, a zero-gravity human-waste disposal system (a space toilet) to be used in the International Space Station, by buying all of his friends new comic books. However, Howard discovers he made a mistake that will cause the toilet to fail and explode after 10 flushes, so the guys convene to try and fix it (a la Apollo 13 's Ken Mattingly), working for a whole night to find a solution and even testing the toilet with meatloaf which Howard brought from his mother. In the end, the ISS astronauts report to NASA that they are going on an unscheduled "spacewalk", suggesting that Howard failed. While at the comic book store, Stuart tells Leonard that he is having a second date with Penny and asks for advice. Leonard deliberately avoids Stuart's request and gives him bad advice. The next day, Leonard feels guilty and goes to apologize to Stuart. Stuart reveals the date went okay until he and Penny started making out in his car and Penny accidentally called him "Leonard." Recurring character: Kevin Sussman as Stuart Bloom Title reference: The classified "space toilet" that Howard and the guys try to repair.
40	23	"The Monopolar Expedition"	Mark Cendrowski	Eric Kaplan & Richard Rosenstock	May 11, 2009 (2009-05-11)	3T7372	9.81
Sheldon wins a National Science Foundation grant to go on a three-month expedition to the Magnetic North Pole to detect magnetic monopoles and prove the validity of string theory. After some hesitation, he decides to go and wants Leonard, Howard and Raj to come with him; they too initially hesitate as it would mean being locked in a cabin with Sheldon for three months, but finally agree. To prepare, Sheldon and the guys use the freezer at the Cheesecake Factory, however this later proves unnecessary as they discover they are going to spend their time in a warm cabin. On the night before the expedition, Leonard expresses doubts on going as it would mean he would not see Penny for the whole summer. He also thinks that Penny is going to miss him after she gives him a blanket with sleeves and a long hug. The next morning, when Leonard meets Penny again, she claims to simply have wished him a safe trip, but after he closes the door, she sadly whispers "It means I wish you weren't going". The guys arrive in the Arctic and agree to abide to the same rules as in the apartment. Recurring characters: Carol Ann Susi as Mrs. Wolowitz, Brian George as Dr. V.M. Koothrappali and Alice Amter as Mrs. Koothrappali Note: This is the first episode to feature Sheldon saying "Bazinga", which would later become his catchphrase. Title reference: The trip that the guys take to find magnetic monopoles.

References

General references

External links

• The Big Bang Theory at IMDb
• The Big Bang Theory: Season 2 at Rotten Tomatoes