Sheldon: I've loved the theremin from the first moment I heard the original Star Trek theme. And it's been killing me that it just sits in my closet, gathering dust.
Leonard: Sheldon, we're working here!
Sheldon: That's all right. I can barely hear you over my theremin. (Leonard pulls the plug) Well, that was a little uncalled for.
Leonard: No, that was completely called for. We need quiet.
Sheldon: So, your project is more important than mine?
Leonard: Well, seeing as your project is to sabotage my project, yes.
Sheldon: Dont beat around the bush, Leonard. If you dont want me here, just say the word, and Ill leave.
(cut to Sheldon in the hallway outside the apartment)
Sheldon: Could have beaten around the bush a little.

Stuart: Oh, Sheldon, I'm afraid you couldn't be more wrong.
Sheldon: More wrong? Wrong is an absolute state and not subject to gradation.
Stuart: Of course it is. It's a little wrong to say a tomato is a vegetable, it's very wrong to say it's a suspension bridge.

Howard: Hang on, I know a place where you could you stay and earn some money at the same time.
Stuart: Great!
Howard: I just have to warn you: it will involve humiliation, degradation and verbal abuse.
Stuart: So, what's the catch?

Bernadette: Hey, Stuart.
Stuart: *startled* Hey.
Bernadette: Sorry, did I startle you?
Stuart: Yes, but at this point pretty much any customer does.

Sheldon: I'm not saying that all senior citizens that can't master technology should be publicly flogged. But, if we made an example of one or two it might give the others incentive to try harder.

Raj: Ooh, Leonard is going all alpha nerd on Sheldon's ass.

Leonard: I had a great idea. Do you know how we're always having to stop and solve differential equations, like when you're doing Fourier equations or using the Schroedinger equation?
Sheldon: Howard doesn't, he's only an engineer.