Howard: *Noticing Raj peeking through someone's window using the telescope* Oh, Raj, no. Billions of dollars have gone into inventing the Internet and filling it with pictures of naked women, so we don't have to peep through windows.

Sheldon: That's not afternoon. That's prevening.
Howard: What?
Sheldon: It's a time of day I invented. It better defines the ambiguous period between afternoon and evening. Prevening. I'm fairly certain it will catch on as it fills a desperate need.
Raj: Right, okay. What are you doing tomorrow prevening?
Sheldon: Well, tomorrow's Saturday. Saturday night is laundry night, so I'll be spending the prevening pre-sorting and pre-soaking.

Zack: Cool, it's gonna be in 3-D!

Wolowitz: Good God, what have we done?

Amy: You should also know that all physical contact, up to and including coitus, is off the table.
Sheldon: May I buy you a beverage?
Amy: Tepid water please.
Wolowitz: My God, what have we done?

Raj: I'm telling you, dude. The only way to feel better about Penny going out with other guys is for you to get back on the whores.

Raj: The Good Wife is on. I tell you, this is my new Grey's Anatomy.

Leonard: So, how'd you two guys meet?
Zack: My company designs the menus for the Cheesecake Factory.
Leonard: Your company?
Zack: Well, it's my dad's, but me and my sister are VPs.
Leonard: So, menus?
Zack: I know it sounds easy but there's a lot of science that goes in designing them.