Sheldon: When do you evacuate your bowels?
Leonard: When I have to.
Sheldon: When you have to? I'm sorry I don't rent to hippies.

Penny: Come on, I mean, you're not upset that your marriage is over?
Beverly: Well, initially I felt something akin to grief and perhaps anger, but that's the natural reaction of the limbic system to being betrayed by a loathsome son of a bitch.
Penny: Sure, sure.

Leonard: Merry Newtonmas everyone.

Raj: Okay, just to be clear, roller skating was my idea, and I'm very unhappy that you turned it into a double date. I hope you both fall on your asses and break your coccyxes.
Sheldon: The plural of coccyx is coccyges.
Raj: Screw you. Give me back my lima beans.

Penny: Whatcha doin'?
Sheldon: I'm attempting to view my work as a fleeting peripheral image so as to engage the superior coliculus of my brain.
Penny: Interesting. I usually just have coffee. Have you been up all night?
Sheldon: Is it morning?
Penny: Yes.
Sheldon: Then I've been up all night.

Leonard: I know what you're doing.
Sheldon: You do?
Leonard: You're using chocolate as a positive reinforcement for what you consider is a correct behavior!
Sheldon: Very good. Chocolate?

Zack: Cool, it's gonna be in 3-D!

TV Announcer: Up next Babylon 5.
(Sheldon looks at Leonard)
(Penny listening to Sheldon and Leonard argue from her apartment)
Leonard: You're not even watching it.
Sheldon: I can hear it.
Leonard: The dialogue offends you?

Penny: Sheldon, you know, I do understand what you're going through.
Sheldon: Really? Did you just have the Nobel Prize in Waitressing stolen from you?

Sheldon: Thank you Kripke for depriving me of the opportunity to share my news with my friends.
Kripke: My pleasure.
Sheldon: My thank you was not sincere.
Kripke: Hmm, but my pleasure is.

Sheldon: You hit me. I'm bleeding.

Leonard: What was that?
Penny: Sheldon tried to steal the ring so I punched him.
Leonard: That's my girl!

Wil Wheaton: What's wrong with him?
Stuart: Everybody has a different theory.

Leonard: I've always been a little confused about this. Why don't Hindus eat beef?
Raj: We believe cows are gods.
Sheldon: Not technically. In Hinduism, cattle are thought to be like God.
Raj: Do not tell me about my own culture, Sheldon! In the mood I'm in, I'll take you out, I swear to cow!

Leonard: Think about what this represents. The fact that we can do this is the only way of definitively proving that there are man-made objects on the moon, put there by a member of a species that only 60 years before had just invented the airplane.
Zack: What species is that?