Penny: Well, a relationship is more complicated than a french fry.
Sheldon: Not according to the work of Berscheid, Snyder & Omoto.
Penny: Oh, what did those rascals do now?

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

Leonard: What am I supposed to do?
Penny: Err, keep your mouth off other women.

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

Sheldon: Ignore them, Amy. They're just jealous because they'll never have a relationship as good as ours.
Penny: Isn't this when he says "bazooka" or something?

Penny: You guys are going out two nights in a row?
Sheldon: I missed a number of date nights while I was on my train trip, and I'm contractually obligated to make them up under the terms of the relationship agreement.
Penny: That's so hot.
Amy: It's better than hot, it's binding!

Leonard: I've seen you guys ignore each other for hours, doing totally different things.
Sheldon: It's called parallel play.
Leonard: Yeah, toddlers do that.
Sheldon: Not as well as we do.