Sheldon: I believe you know why I'm here.
Penny: I always figured it was to study us, discover our weaknesses, and report back to your alien overlords.

I'd take Sheldon to Switzerland, absolutely. And I'd leave him there.

Wolowitz

Instead of underpants, I covered my crotch with potato salad this morning. Thoughts?

Leonard

Given that St. 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

Sheldon: Do you recognize this?
Leonard: Not the roommate agreement!
Sheldon: Indeed, the roommate agreement. I call your attention to the friendship rider in Appendix C: Future Commitments, Number 37. In the event one friend is ever invited to visit the Large Haldron Collider, now under construction in Switzerland, he shall invite the other friend to accompany him.
Leonard: For god's sake!
Penny: You actually put that in an agreement?
Leonard: We also put in what happens if one of us gets a MacArthur grant, or if one of us gets super powers, or if one of us turns into a zombie.
Sheldon: He can't kill me, even if I turned.
Penny: Ts there anything in there if one of you gets a girlfriend?
Sheldon: No, that seemed a little far fetched.

Penny: We're going to Disneyland and ride the Matterhorn?
Leonard: How does that involve air travel?
Penny: We're going to Disney World and ride the Matterhorn?

Leonard: This tray contains clues as to what you and I are going to be doing on Valentine's Day.
Penny: Wow okay, let's see. We got milk chocolate, Swiss cheese, fondue... my lactose intolerant boyfriend is going to eat all this and I'm going to climb on your back and rocket to the moon?

The Big Bang Theory Season 3 Episode 15 Quotes

Penny: We're going to Disneyland and ride the Matterhorn?
Leonard: How does that involve air travel?
Penny: We're going to Disney World and ride the Matterhorn?

Leonard: This tray contains clues as to what you and I are going to be doing on Valentine's Day.
Penny: Wow okay, let's see. We got milk chocolate, Swiss cheese, fondue... my lactose intolerant boyfriend is going to eat all this and I'm going to climb on your back and rocket to the moon?