The Big Bang Theory / Season Four
Sheldon begins an odd relationship with his female counterpart, Amy Farrah Fowler. Penny struggles with the realization that it's hard for her to appreciate dumb guys after dating Leonard. Leonard begins dating Raj's sister Priya. Howard and Bernadette get engaged.
- Animal Hoarding: After Amy breaks up with him, Sheldon starts collecting cats.
- Continuity Snag: When Leonard wanted to have a cat in the second season (The Fuzzy Boots Corollary), Sheldon was allergic to them. Leonard found a breeder who had hypo-allergenic ones.
- The Bus Came Back: Bernadette never actually left, she and Howard just stopped dating. But it is realistic in how people would avoid each other in situations like that.
- Cavemen vs. Astronauts Debate: In the ninth episode, the guys debate who the bravest person in the Marvel Universe is.
- Continuity Nod: Leonard asks Howard to honor the girlfriend pact, which was first revealed in season three and how Howard met Bernadette.
- A Date with Rosie Palms: Howard unwisely uses his robot hand for this. Twice.
- Groin Attack: On "The Zarnecki Incursion", Penny knees the guy who stole Sheldon's World of Warcraft account.
Penny: Today's the day a girl is finally going to touch you in your little special place.
- Have You Tried Rebooting?: How the hospital receptionist frees Howard from his robotic hand in "The Robotic Manipulation".
- Pet's Homage Name: Sheldon names his cats after the scientists involved in the Manhattan Project.
- Odd Name Out: All except for Zazzles - because he's just so zazzy!
- Romantic False Lead:
- A classical version in the form of Priya. It really doesn't help that she is highly educated and more of a match for Leonard on an intellectual level.
- Zach also takes on this role, although played around with extensively in that he was friendly with the guys and Penny admitted she didn't have much feelings for him.
- Weirder Than Usual: In one episode, Sheldon and Amy terminate their friendship, and he tries to hide his loneliness by adopting first one cat, then several more. Leonard tries to express his concern to Raj and Howard, who at first don't understand the problem when he says he's worried about Sheldon. Howard notes that they are always worried about Sheldon, whom they described in an earlier episode as being "one lab accident away from a supervillain." After interacting with him and the first cat, Dr. Robert Oppenheimer, they have a better grasp of the situation.
Howard: Okay, I get it. We're worried about Sheldon.
- Wham Episode: Raj and Penny waking up in bed together, which had ramifications that could tear the group apart.