Penny hosts a Halloween party putting Leonard, Sheldon, Wolowitz and Koothrappali through a new test of their social skills. ..More

With Wolowitz AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team. ..More

Raj's parents set him up on a blind date, and when he discovers he can talk to her, she shows interest in Sheldon. ..More

When they're invited to present at a physics conference, Sheldon's reluctance to share the credit leads to a tiff between him and Leonard, and Penny's intervention only exacerbates the situation. ..More

Leonard and Sheldon each lie to avoid hearing Penny sing in a production of Rent. However, Sheldon's lie becomes a bit too complicated for its own good. ..More

With his friends knowing how sour he acts when sick and avoiding him as a result, Sheldon is nursed for by Penny, who hasn't a clue what she's in for. ..More

With Sheldon rattled and impossible to be around after meeting Dennis, a 15-year-old physicist who's smarter than he, the rest of the guys search for a way to eliminate the threat. ..More

Sheldon finds himself booted from the gang's Physics Bowl team and replaced with Leslie so he forms his own team hoping to prove he's superior. ..More

When the delivery of a full-size prop of 1960's The Time Machine makes Penny miss work, she scolds Leonard about his sci-fi collectibles. He decides it's time to give up such childish pursuits. ..More

The rest of the gang fall for Sheldon's twin sister, and Leonard's plan to win her heart is derailed when Sheldon declares he'll be the one to decide who can date her. ..More

Penny wants to throw a surprise party for Leonard but Sheldon's indulgence at an electronics store throws her off-track. ..More