Sheldon: [jumps out of the sofa] Bazinga, punk. Now we're even!

Sheldon: I am also a son of the Lone Star state. I'm Texas through and through. And we know how to settle scores down there. If you doubt me, just ask Mexico.

Sheldon: You know, the German philosopher Friedrich Nietzsche believed that morality is just a fiction used by the herd of inferior human beings to hold back the few superior men.
Leonard: Thanks, that actually does help.
Sheldon: It's worth noting that he died of syphilis.

Sheldon: "See you in hell Sheldon"? The most frightening thing about that is the missing comma.

Sheldon: Come on out, merry pranksters. Take a bow!

Howard: You should've seen the look on your face!
Sheldon: Oh, yes. The slightly widened eyes of mildly startled.

Sheldon: And reverse the spin on the anti-proton, and gamma becomes alpha multiplied by a matrix of I comma zero. And there we have it, conclusive proof that I am absolutely useless after nine o'clock.

Sheldon: You can lead a chicken to crisco, but you can't make your mother fry it.

Sheldon: Frankly, Mom, I'm encouraged to see how advanced your group has become -- willing to sail into the ocean without fear of falling off the edge.

Sheldon: There's a lot of harm in trying something new. That's why we test out drugs and cosmetics on bunny rabbits.

Sheldon: Does this mean you're not going to sing Soft Kitty?
Mary: No, I will always sing you Soft Kitty. [sings] Soft kitty, warm kitty, little ball of fur…
Leonard: [opens door] Mrs. Cooper, were we supposed to take that pie out of the oven?
Sheldon: Get out!
Mary: Well, that was rude.
Sheldon: Well, I know, but he means well. Sing.
Mary: [sings] Happy kitty, sleepy kitty…
Sheldon: What are you trying to pull, Mom? From the top.
Mary: [to God] This is what I'm talking about. [sings] Soft kitty, warm kitty, little ball of fur…

Sheldon: You just got off the list, would you like back on it?

Sheldon: This will just take a moment, it's on a five and a quarter inch floppy.
Amy: A floppy disk?
Sheldon: Well, I started the list when I was nine.

Sheldon: Until you either do not go or go to Wil Wheaton's party you are simultaneously my friend and not my friend. I'm characterizing this phenomenon as Schrodinger's Friendship.

Leonard: It's from Game of Thrones. What do you think?
Sheldon: I don't know. If we're going to start a fantasy sworld collection, and I've long thought we should, is this really the sword to start with?
Leonard: What did you have in mind?
Sheldon: Well, off the top of my head, I'd have to go with Excalibur. It gives you the right to rule England.
Leonard: It would be a replica of a movie prop.
Sheldon: Fair enough. It'd give you the right to rule a replica of England.