Sheldon: And of those few months, how long have you been a demented sex pervert?

Raj: I don't like bugs, okay. They freak me out.
Sheldon: Interesting. You're afraid of insects and women. Ladybugs must render you catatonic.

Sheldon: Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and as it always has, rock crushes scissors.

Sheldon: Why are you crying?
Penny: Because I'm stupid.
Sheldon: That's no reason to cry. One cries because one is sad. For example, I cry because others are stupid, and that makes me sad.

Leonard: You don't go into science for the money.
Bernadette: Speak for yourself. Last month my company both invented and cured restless eye syndrome. Ka-ching, ya blinky chumps!

Raj: It's too late. He's been murdered by someone in this room. Welcome to another classic Koothrappali murder mystery dinner.
Amy: I'm leaving.

Sheldon: Well then why are you doing it?
Mary: Because I'm not perfect, Shelly. And that man's booty is.