Sheldon: I need your help in a matter of semiotics.
Penny: What?
Sheldon: Semiotics, the study of signs and symbols as a branch of the philosophy related to linguistics.
Penny: Okay, honey, I know you think you are explaining yourself, but you're really not.

Leonard: If I take it off, Sheldon wins.
Penny: Sweetie, every night you don't kill him in his sleep, he wins.

Penny: I mean, who even reads Scientific American?
Leonard: It's kind of a big deal.
Penny: If it's such a big deal, how come the biggest celebrity they could get for the cover is a molecule?

Howard: I'm not signing a prenup.
Penny: All right, Howard Wolowitz, listen up! You sign anything she puts in front of you, because you are the luckiest man alive. If you let her go, there is no way you can find anyone else. Speaking on behalf of all women, it is not going to happen, we had a meeting.

Sheldon: Who do I speak to about permanently reserving this table?
Penny: I don't know, a psychiatrist?

Leonard: If Penny didn't know that Leslie had already turned me down then that would unambiguously mean that she, Penny, thought I should ask her, Leslie, out, indicating that she, Penny, had no interest in me asking her, Penny, out but because she did know that I had asked Leslie out and that she, Leslie, had turned me down then she, Penny, could be offering me consolation. "That's too bad, you would have made a cute couple" but while thinking "good, Leonard remains available."
Sheldon: You're a lucky man Leonard.
Leonard: How so?
Sheldon: You're talking to one of three men in the western hemisphere capable of following that train of thought.
Leonard: Well, what do you think?
Sheldon: I said I could follow it, I didn't say I cared.

Sheldon: I don't know what the protocol is here. Do I stay, do I leave? Do I wait to greet them with a refreshing beverage?
Penny: Gee, Sheldon, you're asking the wrong girl. I'm usually on the other side of the tie.