Leonard: All right, you brought this on yourself. Sheldon, get him.
Sheldon: If a zombie bites you, you turn into a zombie. However, if a mummy bites you, all you turn into is some schmo with a mummy bite. So, like a zombie that's been eaten from the waist down, you, sir, have no leg to stand on.

Sheldon: Therefore, the timeline in which 1955 Biff gets the almanac is also the timeline in which 1955 Biff never gets the almanac. And not just never gets, never have, never hasn't, never had have hasn't.

Penny: Why would they lie to us?
Sheldon: That's a good question.
*Sheldon knocks three times on the restaurant window* Amy and Bernadette! [x3]
Sheldon: Why did you lie to us?

Sheldon: This place could really use a suggestion box.

Sheldon: Amy's sick.
Leonard: Aww, what's wrong with her?
Sheldon: Well, she talks a lot. Always wants to hold hands.
Leonard: That's not what I meant.
Sheldon: Well, if you were referring to her illness, your question should have been "What ails her?"
Leonard: What ails her?
Sheldon: Oh, who knows.

Sheldon: Why do we have a geology book? Leonard, did you throw a children's party while I was in Texas?

Howard: He can't handle the fact that I'm a bigger deal than he is now.
Sheldon: Oh, preposterous. I have been solely responsible for this university's six loop quantum gravity calculations, I have changed the way we think about Bose-Einsten condensates, and I am also the one who got Nutter Butters in the cafeteria vending machine. Maybe you missed that news while you were floating around like a goof in outer space.

Sheldon: Now, back to our game.
Raj: You were in the middle of an erection.
Sheldon: Oh, of course. It's right here in my hand.

Raj: Okay. How about a little Miley Cyrus next?
Sheldon: Who's he?

Mike: How do you not make a first down there?
Sheldon: They passed against a nickel defense. They should have run it off tackle.
Mike: How the hell do you know that?
Sheldon: My father loved football. He always made me watch it before I was allowed to do my homework.

Sheldon: As hard as this is I have to move on. I can't keep postulating multi-dimensional entities and get nothing in return. I have needs too!

Employment adviser: So, Mr. Cooper, you're looking for a job?
Sheldon: A menial job. Like yours.
Employment adviser: Why thank you for noticing. I'm Menial Employee of the Month.

Sheldon: Pick a card, Sheldon. Now look at it and put it back in the deck. Now do you remember your card? Of course I do, I have an eidetic memory.

Sheldon: I also was certain HD-DVD would win out over Blu-ray.
Amy: How old were you then?
Sheldon: Old enough to know better!

Sheldon: We're scientists, we can conduct our own research. I propose that we imprison two street people-
Amy: No.
Sheldon: You didn't even let me finish.
Amy: Forget it.
Sheldon: Oh, so you can experiment on all the apes you want, but I want to manipulate the emotions of two captive human beings, suddenly I'm the monster.