Penny: Alright, look, a tie on the doorknob usually means someone doesn't want to be disturbed because they’re, you know, getting busy.
Sheldon: So you're saying Leonard has a girl in there.
Penny: Well, either that or he's lost his tie rack and gotten really into Bryan Adams.

Sheldon: Woman, you are playing with forces beyond your ken.
Penny: Yeah, well your Ken can kiss my Barbie.

Raj: [to Amy] If you were having Sheldon's baby, would you really want him in the room?
Penny: Yeah, if he's in the room when they're making the baby, I'll give you $10.

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

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.