Raj: No, no, no, no! That rate is much too low for what we'd expect from this collision. Do you understand that we're talking about dark matter colliding in outer space?
Sheldon: Of course I understand. And who are you to tell me about outer space?
Raj: I'm the astrophysicist. Astro means space.
Sheldon: Astro means star.
Raj: Okay, well, let me just tell you, if we were having this argument in my native language, I'd be kicking your butt.
Sheldon: English is your native language.

Raj: My god, you think that every thought that comes out of your head is pure gold. Well, let me tell you something. Some of those thoughts are pure caca.
Sheldon: Caca?
Raj: It means doo-doo.

Sheldon: Wait, you have to drive me home.
Raj: How did you get here?
Sheldon: I walked.
Raj: So walk home.
Sheldon: I can't. There's a big dog outside.

Penny: What's this cartoon called again?
Leonard: Oshikuru: Demon Samurai.
Sheldon: And it's not a cartoon, it's anime.

Penny: I give up. He's impossible.
Sheldon: I can't be impossible; I exist. I think what you meant to say is, 'I give up; he's improbable'.

Penny: Oh man, did the KISS Army repeal "Don't Ask, Don't Tell"?

Wolowitz: They're called tattoo sleeves. Put them on, have freaky sex with some freaky girl with her business pierced, take them off, and I can still be buried in a Jewish cemetery.

Wolowitz: Yes, she's pushy, and yes, he's whipped, but that's not the expression.

Leonard: Okay, I know what you're doing.
Sheldon: Really?
Leonard: Yes, you're using chocolates as positive reinforcement for what you consider correct behavior.
Sheldon: Very good. Chocolate?
Leonard: No, I don't want any chocolate! Sheldon, you can't train my girlfriend like a lab rat.
Sheldon: Actually, it turns out I can.

Sheldon: Interesting. Sex works even better than chocolate to modify behavior. I wonder if anyone else has stumbled onto that.

Girl: What are you gonna get, Raj?
Raj: With my luck, hepatitis.

Sheldon: You know, I've always wanted to go to a goth nightclub.
Howard: Really?
Sheldon: Bazinga! You never see any of my practical jokes coming, do you?

Leonard: I'm just saying, you catch more flies with honey than with vinegar.
Sheldon: You catch even more with manure, what's your point?

Leonard: They're gonna get beaten up at that club.
Penny: They're gonna get beaten up at Walgreens.

Sheldon: Penny, while I subscribe to the "Many Worlds" theory which posits the existence of an infinite number of Sheldons in an infinite number of universes, I assure you that in none of them am I dancing.
Penny: Are you fun in any of them?
Sheldon: The math would suggest that in a few I'm a clown made of candy. But I don't dance.