Amy: What are you doing here?
Sheldon: I'm here to return your belongings. That's what people who've broken up do.
Amy: And you didn't do your compulsive knocking ritual so I'd open the door?
Sheldon: On the contrary, you no longer get to enjoy my charming eccentricities. We're not friends with benefits.

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.

Sheldon: Thankfully all the things my girlfriend used to do can be taken care of with my right hand.

Sheldon: Hello.
Leonard: Hey, buddy, can we have some privacy?
Sheldon: Of course. Wouldn't want to intrude. (takes red bra out of his pocket and hands it to Penny) This is yours.
Penny: Okay, when I'm done with him, I'm gonna need more information.
Sheldon: Nothing odd. I just wanted to rub Amy's nose in it.

Leonard: I'm not being weird. Am I being weird?
Sheldon: Yes. And that's coming from me.