When Penny's big acting break on NCIS is a bust, Leonard struggles to help her, which results in Penny asking Leonard a bold relationship question.
After Amy ruins one of Sheldon's favorite movies – Raiders of the Lost Ark – he gets defensive, seeking revenge.
Meanwhile, Leonard discovers a way to get Penny to do anything; and Raj and Stuart create online dating profiles.
Sheldon must decide how much "Amy time" is too much after she takes a job at his university, and their relationship is put to the test.
Meanwhile, Howard finds himself sleeping on Raj's couch after a fight with Bernadette.
Sheldon's latest scientific breakthrough makes him feel like a fraud – and threatens to haunt him forever.
Meanwhile, Howard's romantic gesture to Bernadette causes Penny to step up her game with Leonard.Sheldon feels slighted when Professor Proton (recurring guest star Bob Newhart) seeks advice from Leonard instead of him, and he seeks revenge by befriending a rival science TV host, Bill Nye (guest starring as himself).Meanwhile, Raj gets jealous when Howard crashes "girls' night."Leonard tries to keep Sheldon from overreacting when a past mistake comes to light, but Sheldon punishes Leonard by making him "walk a mile in his shoes." Meanwhile, Penny confronts Raj's ex-girlfriend, Lucy (guest star Kate Micucci).Doctors Leonard Hofstadter & Sheldon Cooper (Johnny Galecki & Jim Parsons) are brilliant physicists – masterminds of their Cal Tech laboratories, but socially challenged in the non-theoretical real world.Enter beautiful, street-smart neighbor, the actress/waitress Penny (Kaley Cuoco), who aims to teach them a thing or two about life.Despite their on-again, off-again relationship in the past, Leonard believes he’s found true love with Penny.