2x1 22 Sept 2008 The Bad Fish Paradigm Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant. 2x2 29 Sept 2008 The Codpiece Topology A jealous Leonard reacts to Penny's new guy by rebounding with Leslie. 2x3 6 Oct 2008 The Barbarian Sublimation Sheldon creates a monster when he introduces Penny to online gaming. 2x4 13 Oct 2008 The Griffin Equivalency Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article. 2x5 20 Oct 2008 The Euclid Alternative Leonard and his friends stage an intervention to force Sheldon to face his fear of driving. 2x6 3 Nov 2008 The Cooper-Nowitzki Theorem Sheldon and the gang are confused when a young grad student is attracted to him. 2x7 10 Nov 2008 The Panty Piñata Polarization When Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate. 2x8 17 Nov 2008 The Lizard-Spock Expansion Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life. 2x9 24 Nov 2008 The White Asparagus Triangulation Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards. 2x10 8 Dec 2008 The Vartabedian Conundrum Leonard asks Penny for advice when his new relationship starts moving too fast. 2x11 15 Dec 2008 The Bath Item Gift Hypothesis Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette. 2x12 12 Jan 2009 The Killer Robot Instability Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for. 2x13 19 Jan 2009 The Friendship Algorithm Sheldon creates a scientific procedure for making friends. 2x14 2 Feb 2009 The Financial Permeability Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend. 2x15 9 Feb 2009 The Maternal Capacitance Leonard and Penny are drawn together after a disastrous visit from Leonard's mother. 2x16 2 Mar 2009 The Cushion Saturation A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz. 2x17 9 Mar 2009 The Terminator Decoupling Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress (Summer Glau) is on board the train they are taking to San Francisco. 2x18 16 Mar 2009 The Work Song Nanocluster Penny's home business turns into a complete nightmare when Sheldon takes over. 2x19 30 Mar 2009 The Dead Hooker Juxtaposition Penny squares off with a new beautiful female neighbor who may become the building's "new Penny." 2x20 13 Apr 2009 The Hofstadter Isotope A fellow comic book enthusiast's hitting on Penny leads to Leonard and Howard going to a bar's Ladies' Night. 2x21 27 Apr 2009 The Vegas Renormalization Leonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny. 2x22 4 May 2009 The Classified Materials Turbulence Penny's second date with Stuart sees her making a comment that gives Leonard new hope for a relationship with her. Wolowitz realizes there's a crucial error in a NASA project he's working on. 2x23 11 May 2009 The Monopolar Expedition The guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.