Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
After seeing Penny with a handsome new guy, Leonard rushes into a rebound relationship with Sheldon's nemesis, Leslie Winkle.
Sheldon creates a monster when he introduces Penny to online gaming.
Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.
Sheldon and the gang are confused when a young grad student is attracted to him.
When Sheldon bans Penny from the apartment for a series of petty infractions, Penny vows to get revenge.
Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.
Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.
Leonard asks Penny for advice when his new relationship starts moving too fast.
Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.
When Penny's comment about Wolowitz's love life sends him into a depressed stupor, his friends lose their most important teammate in an upcoming fighting-robot competition.
Sheldon develops a scientific procedure for making friends; Kripke controls a new supercomputer.
Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.
Leonard and Penny are drawn together after a disastrous visit from Leonard's mother (Christine Baranski).
A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.
Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress (Summer Glau) is aboard the train they are taking to San Francisco.
Penny's home business turns into a complete nightmare when Sheldon takes over.
Penny develops a rivalry with a sexy new female neighbor who threatens her position as queen bee of the building.
Wolowitz and Leonard decide to check out a local bar on Ladies' Night.
Koothrappali and Leonard take Wolowitz to Las Vegas; Sheldon is forced to bunk with Penny when he gets locked out of his apartment.
Penny makes a surprising revelation about Leonard while on her date with Stuart; Wolowitz finds a critical design flaw in his NASA project.