Penny asks Leonard to lie to her visiting father, while Howard, Raj and Bernadette spend all night looking through a telescope. ..More

Amy crushes on one of Penny's dim ex-boyfriends, Zack. Raj and Wolowitz argue over who'd be the better superhero. ..More

The guys get Zack and Penny to join their Justice League costume for a New Year's Eve bash at the comic book store. ..More

Their friendship becomes strained when Sheldon tries to take over Leonard's creation of a smartphone application that solves differential equations. ..More

Howard is jealous when Bernadette runs into her old boyfriend at a science event they're attending. ..More

Amy and Bernadette accuse former party girl Penny of becoming a party pooper when she lets an email from work impact their girls' weekend in Las Vegas. Meanwhile, the guys brainstorm about inventing something cool. ..More

Sheldon and Raj undertake an underground research expedition that turns into a test of how long before they get under each other's skin. Meanwhile, Leonard and Penny argue about money. ..More

Penny's flirtatious sales pitch leaves a doctor-client smitten and the guys must pitch in to help her deal with him, while, Bernadette and Amy debate whether female scientists ought to play the sexuality card. ..More

Leonard needs surgery for a deviated septum, and Sheldon gets his nose out of joint because he feels an operation is too dangerous and that his roommate may not make it out alive. ..More

It's a banner day for Sheldon as he bids a sad farewell to his Fun With Flags podcast. Meanwhile, Leonard, Howard and Raj probe a late professor's research in search of some hidden significance. ..More