Penny: Okay, this is about science. Why'd you come to me?
Sheldon: Well, because it's also about my reputation. And somehow you manage to hold your head high despite your checkered past.
Penny: Checkered past?
Sheldon: It's a figure of speech referring to how sexually promiscuous you were.
Penny: Really? Well, I've got a figure of speech about how sexually promiscuous you can go be with yourself.

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: They're very different. Physics answers the question: what is the nature of the universe? Geology answers the question: you know, what'd I just trip over?

Raj: Are you saying that you don't believe two people fall in love?
Ruchi: Of course they do. It's just that what people call "love" is actually a series of biochemical reactions in the brain that fade over time.
Raj: Yes. Like the old song, "When a man has a biochemical reaction for a woman."

Sheldon: I've been modeling different types of dark matter and the traces they would leave on the zircon inside your meteorite.
Bert: What's this one here?
Sheldon: That's actually a dark matter model of my own creation. I call it the Cooper Boson.
Bert: Cool. I got to name a rock once. I named it Moderately Sedimented Shale. Guess I kind of pooped the bed on that one.