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'.

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: 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?

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.

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.

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.

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

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

Sheldon: That does smell good, too bad it's Monday.

Leonard: Sheldon, you need to find a better way of dealing with Penny.
Sheldon: What am I supposed to do? Eat French Toast on a Monday? Now that would be impossible.

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.

Penny: Ok, who wants syrup & who wants powdered sugar?
Sheldon: I want oatmeal.
Penny: Well, I want a boyfriend whose roommate isn't a big pain in the ass.
Sheldon: I'm sure that will happen soon enough.