Leonard: Cause of death for Uncle Carl was KBB? What's KBB?
Sheldon: Killed by badger.
Leonard: How's that?
Sheldon: It was Thanksgiving. Uncle Carl said, "I think there's a badger living in our chimney. Hand me that flashlight." Those were the last words he ever spoke to us.

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".

Howard: Okay, give me the flowers and pie.
Sheldon: But if we show up and you're holding them, she'll think they're only from you.
Howard: They are only from me. You said the gift of you was enough.
Sheldon: Yes, but now that I've seen what the gift of me with flowers and pie looks like there's no going back.

Leonard: Wow, Donkey Kong. This was my game when I was a kid.
Sheldon: Because it's a story of a pretty blonde girl tirelessly pursued by a small oddly-shaped man?

Howard: Are you familiar with the Drake Equation?
Sheldon: The one that estimates the odds of making contact with extraterrestrials by calculating the product of an increasingly restrictive series of fractional values such as those stars with planets, and those planets likely to develop life? N equals R times FP times NE times FL times FI times FC times L?
[pause]
Howard: Yeah, that one.

Sheldon: I know he (Spock) wouldn't care for an outburst of human emotion, but oh goodie, oh goodie, oh goodie!

Penny: What's this cartoon called again?
Leonard: Oshikuru: Demon Samurai.
Sheldon: And it's not a cartoon, it's anime.

Penny: What was my first strike?
Sheldon: March 18th, you violated my rule about forwarding email humor.
Penny: I did?
Sheldon: The photo of the cat who wants to "Has Cheeseburger?"
Penny: Oh, come on, everybody loves Lolcats. They're cute and they can't spell because they're cats.
Sheldon: I trusted you with my email address and you betrayed that trust by sending me internet banality. Strike one. Touching my food. Strike two.

Sheldon: Your check-engine light is on.
Penny: Uh huh.
Sheldon: Typically, that's an indicator to, you know, check your engine.
Penny: It's fine. It's been on for like a month.
Sheldon: Well, actually that would be all the more reason to, you know, check your engine.
Penny: Sheldon, it's fine.
Sheldon: If it were fine, the light wouldn't be on. That's why the manufacturer installed that light, to let you know it's not fine.
Penny: Maybe the light's broken.
Sheldon: Is there a check-the-check-engine-light light?

Sheldon: And you thought the opposite of stupid loser was a Community College Graduate?

Sheldon: You seem to have forgotten the reason we live together is that we're best friends. And I've got your back, Jack.

Leonard: Do you have any ideas?
Sheldon: Yes, but they all involve a Green Lantern and a Power Ring.

Leonard: Well you don't have to worry, we broke up again.
*Sheldon gives awkward look and then throws his papers in the air with one of them landing next to his head.
Sheldon: Do you ever think about other people, Leonard? Do you?

Sheldon: *singing in the tune of "Eye of the Tiger"* It's the eye of the tiger, it's the ear of the bat. It's the whiskers of a catfish and the walrus--
Howard: Hang on. Not that your song isn't terrible-- it is... but how do you mention bats and leave out sonar?
Sheldon: You didn't let me finish. *singing* And also regarding the bat. It has sonar.

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?