Sheldon: Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and as it always has, rock crushes scissors.

Stuart: Oh, Sheldon, I'm afraid you couldn't be more wrong.
Sheldon: More wrong? Wrong is an absolute state and not subject to gradation.
Stuart: Of course it is. It's a little wrong to say a tomato is a vegetable, it's very wrong to say it's a suspension bridge.

Howard: Sheldon, don't take this the wrong way, but, you're insane.
Leonard: That may well be, but the fact is it wouldn't kill us to meet some new people.
Sheldon: For the record, it could kill us to meet new people. They could be murderers or the carriers of unusual pathogens. And I'm not insane, my mother had me tested.

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

Raj: Well, I'm a Hindu. My religion teaches that if we suffer in this life we are rewarded in the next. Three months at the North Pole with Sheldon and I'm reborn as a well-hung billionaire with wings.

Barry Kripke: We're all pathetic and creepy, and can't get girls. That's why we fight robots.

Raj: Isn't there a policy against dating graduate students?
Leonard: No, if you can talk to them, you can ask them out.
Raj: Damn, there's always a catch.

Wolowitz: Penny, let me take this opportunity to point out that you are looking particularly ravishing today.
Penny: Not with a thousand condoms, Howard.
Wolowitz: So there is a number.

Leonard: OK, is everyone clear on the plan?
Howard: Yes, Koothrappali's going to wet himself, I'm gonna throw up, Sheldon's gonna run away and you're going to die. Shall we synchronize our watches?

Leonard: [to a "smiling" Sheldon] We're here to see Koothrappali, not kill Batman.

Howard: [looking at his caller ID] Ooh, looks like I'm gonna have sex tonight. [answering phone] Hey, baby...
Penny: His right hand is calling him?

Wolowitz: If it's "creepy" to use the Internet, military satellites, and robot aircraft to find a house full of gorgeous young models so I can drop in on them unexpected, then fine, I'm "creepy".

Mrs. Wolowitz: Want me to get you a popsicle?
Howard: Cherry, please!
Mrs. Wolowitz: I ate the cherry. All that's left is green.
Howard: You make me wanna kill myself!

Penny: Here you go, [to Leonard] quesadilla, [to Howard] salad, [to Raj] here's your pizza. And thanks to Sheldon's heated discussion with my manager, one barbecue bacon cheeseburger, barbecue sauce, bacon, and cheese on the side.
Sheldon: Thank you!
Penny: Go ahead. Eat it. I dare you!

Leonard: Howard, this is big science. You could be the engineer who builds the equipment that puts us on the cover of magazines.
Howard: I could also be the engineer who builds the crossbow that kills Sheldon.