Sheldon: Yes, since their relationship became carnal, Penny has updated his designated term of endearment, distinguishing him from those she calls 'sweetie,' usually as an attempt to soften a thinly-veiled insult.
Penny: You're boring people, sweetie.
Sheldon: Although sometimes, she omits the veil entirely.

Sheldon: Excuse me. Wolverine Origin, mini series issue two, page 22, retractable bone claws. You know, if you three spent less time thinking about sex and more time concentrating on comic books, we would have much less of these embarrassing moments.

Sheldon: I am not crazy, my mother had me tested.

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

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'.

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.

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

Sheldon: For what it's worth, my mother says that when we deceive for personal gain, we make Jesus cry.

Sheldon: Yeah, I have to say I thought the toilet humor would get less funny with repetition. Apparently there is no law of diminishing comedic returns with space poop.

Leonard: I don't think I can go to the North Pole.
Sheldon: OK, Leonard, I know you're concerned about disappointing me, but I want you to take comfort from the knowledge that my expectations of you are very low.

Sheldon: Leonard, you may be right. It appears that Penny secretly wants you in her life in a very intimate and carnal fashion.
Leonard: You really think so?
Sheldon: Of course not. Even in my sleep-deprived state, I've managed to pull off another one of my classic pranks. Bazinga!

Sheldon: Howard, you know me to be a very smart man. Don't you think that if I were wrong, I'd know it?

Raj: I don't like bugs, okay. They freak me out.
Sheldon: Interesting. You're afraid of insects and women. Ladybugs must render you catatonic.

Sheldon: You know I'm in such a good mood I'm actually finding your tenuous grasp of the English language folksy and charming today.

Sheldon: Penny.
Penny: What?
Sheldon: I can't sleep.
Penny: Maybe that's because your hole is still open.