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

Leonard: If I take it off, Sheldon wins.
Penny: Sweetie, every night you don't kill him in his sleep, he wins.

Penny: Sheldon, what did we say about being a nicer friend?
Leonard: Thank you.
Penny: Leonard, what did we say about being a gullible weeny?

Sheldon: Woman, you are playing with forces beyond your ken.
Penny: Yeah, well your Ken can kiss my Barbie.

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: 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.

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".