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.

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: 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.

Sheldon: Why are you crying?
Penny: Because I'm stupid.
Sheldon: That's no reason to cry. One cries because one is sad. For example, I cry because others are stupid, and that makes me sad.

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!

Sheldon: There's a fine line between wrong and visionary. Unfortunately, you have to be a visionary to see it.

Rajesh: Okay, please don't take this the wrong way, but I'd rather swim buck naked across the Ganges with a paper cut on my nipple and die a slow agonizing death from a viral infection, than work with you.