In the seventh series finale, Sheldon becomes upset about his career, the destruction of the comic-book store and Leonard and Penny's future living arrangements.
Elsewhere, Howard is unable to keep hold of a carer for his mother.
Comedy, staring Johnny Galecki, Jim Parsons and Kaley Cuoco Leonard vows to be more self-assured around women, believing his problem attracting a girlfriend stems from a lack of confidence.
Guest starring Eliza Dushku The friends set up camp outside a cinema to get tickets for a new cut of Raiders of the Lost Ark - but find themselves resuming hostilities with Sheldon's old foe Wil Wheaton, the former Star Trek: The Next Generation actor.
Meanwhile, Penny and Bernadette invite Amy to a sleepover Penny's dad pays a visit and Leonard discovers she told her parents they were back together, so he plays his boyfriend role to the hilt - much to her dismay.
Meanwhile, Raj gets drunk and makes a pass at Howard's girlfriend Bernadette.
Guest starring Keith Carradine Amy finds she has romantic feelings for Penny's former boyfriend Zack, while Raj and Howard begin competing to prove which of them would make the better superhero.
Comedy, guest starring Brian Thomas Smith The guys have fun at the expense of Penny's boyfriend Zack, but later try to make amends by enlisting his help with the New Year's costume competition at the comic-book store.
Comedy, starring Kaley Cuoco and Simon Helberg Tension mounts when the gang attends a weekend science conference.
Howard becomes argumentative after Bernadette runs into a former boyfriend, and the fallout causes chaos with the hotel room arrangements.
Rick Fox guest stars, with Simon Helberg and Melissa Rauch Sheldon agrees to participate in a series of short lectures at the university, but is worried the students dislike him.
The following is a list of characters from the American situation comedy The Big Bang Theory created and executive produced by Chuck Lorre and Bill Prady, which premiered on CBS on September 24, 2007.