Sheldon: Okay, stop ruining Valentine's day and order my pizza.

Sheldon: Eat one of your Luna bars. Very often when women think they're angry, they're really just hungry.

Leonard: All right, Sheldon, we're going to Wil's. This is your last chance.
Sheldon: No, Leonard, this is your last chance. One day, a historian is going to come to you and say, is it true you were friends with Dr. Sheldon Cooper? And you're going to have to choke back a hot sob of regret and humiliation as you mumble, I was, but I chose to go to a party thrown by the one kid from Stand By Me that no one remembers.

Wil Wheaton: Oh, was that a doorbell?
Amy: I didn't hear anything.
Wil Wheaton: [doorbell rings] Huh, there it is again. Sheldon, why don't you answer it?
Sheldon: But I don't know who it is.
Wil Wheaton: Maybe it's a special guest who I invited just to surprise you. Why don't you open it up and find out.
Sheldon: This is a terrible message to send to children. Children, you never open the door if you don't know who's on the other side. You always make your mommy or daddy do it while you hide under the bed and try to imagine what your superhero name will be when you avenge their deaths.
Amy: I'll get it.
Sheldon: But it can't be the Silver Shadow. That's mine.

Sheldon: *knock knock knock* Amy.
*knock knock knock* Amy
*knock knock knock* Angry Amy.

Raj: You picked Stuart over one of us?
Sheldon: Well, I wanted to choose one of you, but you all turned against me.
Howard: Picking a best man isn't about keeping score.
Sheldon: But you're all my friends. I mean, if I didn't collect data, how could I possibly choose among the three of you?
Raj: Well, that's actually kind of sweet.
Sheldon: Is it? Well, then, perhaps I said it wrong.

Amy: Okay, imagine you're looking in a mirror. The image you see looks just like you. That's called symmetrical.
Sheldon: Now imagine you have a billion mirrors, and each of them reflects one thing about you correctly and a billion things about you incorrectly. And imagine the set of incorrect things are floating in an abstract n-dimensional hyperspace. Now imagine there was never a mirror to begin with.

Sheldon: I was actually trapped by Penny and forced into reveleaing confidential information about Howard's father.
Leonard: What information?
Sheldon: I can't tell you, I'm bound by closet organizer-organizee confidentiality.
Raj: Just tell us.
Sheldon: Badgering me won't work. What would work is saying Penny would tell us anyway.
Leonard: Then that.
Sheldon: Very well. Everyone's on their game today.

Leonard: I've dated plenty of women. There was Joyce Kim, Leslie Winkle.
Sheldon: Notify the editors of the Oxford English Dictionary. The word plenty has been redefined to mean two.

Penny: The letter was found in Bernadette's closet. Doesn't that count for something?
Sheldon: Are you pointing out that California is a community property state and since Howard and Bernadette are married the intellectual property contained in that letter is jointly owned by the two spouses?
Penny: Yeah, obviously.
Sheldon: Well played. Sometimes I don't give you enough credit, Penny.

Sheldon: I have mixed feelings about interviews. I like the part where I talk, but I do not like the part where the other man talks.

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.

Sheldon: I believe the painful sensation felt after passing a meal of spicy chillies is proof that the rectum does possess the sense of taste.

Penny: I meant has he ever been involved with someone who wasn't a brainiac?
Sheldon: Oh! Well, a few years ago, he did go out with a woman who had a Ph.D in French Literature.
Penny: How is that not a brainiac?
Sheldon: Well, for one thing she was French.

Sheldon: Whenever you're ready, AT&T!