Leonard: What would you guys do if you were me?
Wolowitz: I would take Sheldon to Switzerland.
Leonard: Seriously?
Wolowitz: Absolutely. And I'd leave him there.

Sheldon: It was you. I touched you!
Penny: Happy Valentine's Day.

Sheldon: Hello.
Penny: Hello.
Sheldon: Ok, enough with the friendly banter. I believe you know why I am here.
Penny: Oh, I always figured it was to study us, discover our weaknesses, and report back to your alien overlords.
Sheldon: Yes amusing. Extraordinary intelligence might well appear extraterrestrial to you, but let me be more specific. I believe you know why I am here in the laundry room.

Penny: I think I caught the flu. *Throwing up*. Or the plague!

Sheldon: Given that Saint Valentine was a 3rd century Roman priest who was stoned and beheaded, wouldn't a more appropriate celebration of the evening be taking one's steady gal to witness a brutal murder?

Sheldon: There's an economic concept known as a positional good in which an object is only valued by the possessor because it's not possessed by others. The term was coined in 1976 by economist Fred Hirsch to replace the more colloquial, but less precise "neener-neener".

Raj: If anyone's interested, I'll be spending this Valentine's in the same way I spend every Valentine's. Buying a rotisserie chicken from the supermarket, taking it home, standing over the sink and eating it out of the package with my bare hands like an animal.

Sheldon: I've been dreaming about going to the Large Hadron Collider since I was nine years old.
Leonard: Yeah, well, I've been dreaming about spending Valentine's Day with a girl since I was six.
Sheldon: Shame on you! That's no dream for a scientist.

Leonard: Who's miserable and alone?
Raj: Me.
Leonard: Oh, I used to be like that. Then I got a girlfriend.
Sheldon: In pre-1976 terms, neener-neener.

Leonard: Okay, I know what'll cheer you up, let's play one of your driving games.
Sheldon: All right. This game is called Traitors. I will name three historical figures, you put them in order of the heinousness of their betrayal. Benedict Arnold, Judas, Dr. Leonard Hofstadter.
Leonard: You really think I belong with Benedict Arnold and Judas?
Sheldon: You're right. Judas had the decency to hang himself after what he did.

Howard: So what did you end up doing?
Raj: Not much. Nuked a burrito. Prayed to the Hindu God Urvashi that your bowels would loosen and your penis would droop like a willow tree.

Howard: I understand your point, but given a choice Jews always go with Chinese food.

Leonard: This tray contains clues as to what you and I are going to be doing on Valentine's Day.
Penny: Oh, wow. Okay. Let's see. We've got milk chocolate, Swiss cheese, fondue.
My lactose-intolerant boyfriend is going to eat all this, then I'm going to climb on his back and rocket to the moon?

Leonard: We're going to Switzerland to see the CERN supercollider. And ski. We'll also go skiing.
Penny: We're going skiing in Switzerland?
Leonard: Well, you'll ski, I'll fall. But yeah, we will be in Switzerland for Valentine's Day.

Penny: You actually put that in an agreement?
Leonard: Yeah. We also put in what happens if one of us wins a MacArthur Grant, or if one of us gets superpowers, or if one of us is bitten by a zombie.
Sheldon: He can't kill me, even if I turn.