The Big Bang Theory Wiki

Season 2 of The Big Bang Theory premiered on September 22, 2008, and has 23 episodes. It deals with character development and relationships. Sheldon becoming more and more obsessive. Leonard and Penny's relationship takes a turn for the worse when they temporarily break up and reconcile. 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 remains similar to that of season one in his attempts to seduce women, & lastly Raj manages to briefly communicate an apology to Penny without having consumed alcohol.


Main Cast[]

Recurring Cast[]

Guest Cast[]


Episode (Series) Episode (Season/Ep#) Title Original Air Date Directed By Description
18 201 The Bad Fish Paradigm September 22, 2008 Mark Cendrowski Penny and Leonard return from their date, but she gives him a brush off when he tries to get a second date. She confesses to Sheldon about dropping out of college and he can't take the pressure of keeping her secret.
19 202 The Codpiece Topology September 29, 2008 Mark Cendrowski Sheldon with Penny on the stairs while playing Mario. Penny is dating a new guy, so Leonard jumps at the chance to date Leslie Winkle again. Sheldon hates Leslie and resents being exiled to the staircase to play Mario alone.
20 203 The Barbarian Sublimation October 6, 2008 Mark Cendrowski 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.
21 204 The Griffin Equivalency October 13, 2008 Mark Cendrowski Raj discovers a trans-neptunian planetoid and gets featured in People Magazine as a result. The fame soon goes to his head and he alienates all his friends.
22 205 The Euclid Alternative October 20, 2008 Mark Cendrowski

Leonard is working nights at the university and can't drive Sheldon to work. Sheldon alienates all his possible chauffeurs and is forced to try to learn to drive.

23 206 The Cooper-Nowitzki Theorem November 3, 2008 Mark Cendrowski A grad student, Ramona Nowitzki, begins pushing Sheldon to concentrate all his spare time on his scientific endeavours. The loss of his freedom and leisure time upsets Sheldon but he can't stop her.
24 207 The Panty Piñata Polarization November 10, 2008 Mark Cendrowski Sheldon banishes Penny from the apartment when she accumulates three strikes from him. A war escalates between them.
25 208 The Lizard-Spock Expansion November 17, 2008 Mark Cendrowski A smitten Wolowitz thinks he's found his soul mate—until the woman, Dr. Stephanie Barnett, meets Leonard. Wolowitz invites Stephanie to drive the Mars rover, which winds up stuck in a ditch. Stephanie and Leonard then hitch up, alienating Howard.
26 209 The White Asparagus Triangulation November 24, 2008 Mark Cendrowski 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.
27 210 The Vartabedian Conundrum December 8, 2008 Mark Cendrowski Stephanie Barnett 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.
28 211 The Bath Item Gift Hypothesis December 15, 2008 Mark Cendrowski Wizard physicist and all round hunk David Underhill starts working with Leonard. He soon asks Penny out much to Leonard's distress.
29 212 The Killer Robot Instability January 12, 2009 Mark Cendrowski Howard builds a robot called MONTE (Mobile Omnidirectional Neutralization and Termination Eradicator) to enter into the Southern California Robot Fighting League Round Robin Invitational. When Penny tells Howard what she really thinks of his sleazy come-ons, he is hurt and becames distraught; Leonard makes Penny apologize.
30 213 The Friendship Algorithm January 19, 2009 Mark Cendrowski 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.
31 214 The Financial Permeability February 2, 2009 Mark Cendrowski Penny is short on her rent money and so Sheldon lends her some of his spare cash. She feels guilty about not paying it back and still can't pay her electricity bills. Leonard tries to help and discovers that she paid her an $1800 fine for Kurt. Leonard tries and get the money back for her.
32 215 The Maternal Capacitance February 9, 2009 Mark Cendrowski Leonard's mother (Dr. Beverly Hofstadter) comes to visit. She is a cold, analytical psychiatrist. She drives Penny and Leonard to drink with her psychoanalysis while Sheldon loves her.
33 216 The Cushion Saturation March 2, 2009 Mark Cendrowski Penny accidentally shoots Sheldon's sofa cushion with a paint ball gun. He is deeply disturbed by this turn of events and is not happy with the cushion even once it has been dry cleaned. Meanwhile Howard starts sleeping with Leslie Winkle.
34 217 The Terminator Decoupling March 9, 2009 Mark Cendrowski 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. Also Sheldon must let Penny enter his room to email him a scientific paper.
35 218 The Work Song Nanocluster March 16, 2009 Peter Chakos Penny starts her own business and asks Sheldon for help. The other guys become involved and they end up spending all night trying to ship an order for one thousand “Penny Blossoms”.
36 219 The Dead Hooker Juxtaposition March 30, 2009 Mark Cendrowski A new tenant, Alicia, moves in to the apartment above the guys. Sheldon's only concern is with the noise she might make. Where as the other guys are all too quick to help her out with all her needs. Penny becomes increasingly jealous of the way they treat her and losing her queen bee status.
37 220 The Hofstadter Isotope April 13, 2009 Mark Cendrowski It's "Anything Can Happen Thursday" for the guys and they end up with Penny at the comic book store. She goes on a date with the owner Stuart and Leonard is jealous. He suggests that they all head to a bar to meet women.
38 221 The Vegas Renormalization April 27, 2009 Mark Cendrowski Leslie ends her friends with benefits relationship with Howard. Sheldon suggests the guys go to Vegas to help Howard get over the pain. They do and end up hiring a prostitute to give Howard the Jewish girlfriend role playing treatment.
39 222 The Classified Materials Turbulence May 4, 2009 Mark Cendrowski Howard has designed a special toilet for the International Space Station. He realizes that it is going to malfunction and asks the guys to help him fix it. Stuart has another date with Penny and asks Leonard for advice.
40 223 The Monopolar Expedition May 11, 2009 Mark Cendrowski After Sheldon wakes up the president of Caltech in the middle of the night simply to ask a question, he is offered to spend three months doing research on the North Pole in an attempt to prove the validity of string theory. Leonard, Howard and Raj are first overjoyed and then end up going with him. Penny is very upset about Leonard leaving, but can't tell him that.


Season Two received better ratings than the previous season, with an average of 10 million views per episode.