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.

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?

Wow, that's all you got after you were the most obnoxious person on a double date that included Howard Wolowitz?

Beverly: Your Check Engine light is on.
Penny: Yeah, I gotta put a sticker over that.

Penny: You know, I could use a drink, you want to stop for a drink?
Beverly: Oh, I don't drink.
Penny: I do. I'll teach you.

Sheldon: It's doubtful that his mother will be over-impressed with a woman whose biggest achievement was memorizing the Cheesecake Factory menu.
Penny: Hey, it's a big menu! There's two pages just for desserts!
Leonard: And those specials, they change every day!
Penny: Okay, it's lame when I say it, it's just ridiculous when you pile it on.

Sheldon: It's a bust of Sir Isaac Newton.
Penny: Oh sure, sure. Very Christmasy.
Sheldon: Well, excuse me, it's much more Christmasy than anything you put on the tree.
Leonard: Here we go...
Sheldon: December 25th, 1642. Julian calendar. Sir Issac Newton is born. Jesus, however, was actually born in the summer. His birthday was moved to coincide with the traditional pagan holiday that celebrates the winter solstice with lit fires and slaughtered guts, which frankly sounds like more fun than twelve hours of Church with my mother, followed by fruit cake.

Penny: I always tear up when the Grinch's heart grows three sizes.
Sheldon: Tears seem appropriate. Enlargement of the heart muscle, or hypertrophic cardiomyopathy, is a serious disease which can lead to congestive heart failure.

That's all I know. Oh, wait! Fig Newtons were named after a town in Massachusetts, not the scientist.

Penny: Is that why they're called Fig Newtons?
Sheldon: No. Fig Newtons are named after a small town in Massachusetts. No, don't write that down!

TBBT Quotes

I was expecting applause but I suppose stunned silence is equally appropriate.

Sheldon

Sheldon: Nothing more fun than a paradigm shifting evening of science.
Penny: (to Leonard) And you thought it was soaping me up in the shower.