Sheldon: She befriends them and then lies in wait until they reveal a marketable idea, which she steals and sells to the highest bidder.
Leonard: That's ridiculous.
Sheldon: Oh, is it? Well, let's see you come up with an explanation as to why this woman hangs out with us all the time.
Penny: Oh, great. You know what? I've already mooched dinner off you guys. I don't need to listen to this.
Howard: There's your answer: free food.

Howard: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Howard: Once you're fluent, you'll have a billion more people to annoy instead of me.

Bernadette: Maybe we should get one of those machines to help her up the stairs.
Howard: You mean a forklift?

Sheldon: Sheldon Cooper does not cry.
Howard: That's true, you'd rust.

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.