Raj: No, no, no, no, that rate is much too low for what you'd expect from this collision. Do you understand we're taking about dark matter colliding in outer space?
Sheldon: Yes, of course I understand, and who are you to tell me about outer space?
Raj: Well, I am the astrophysicist! Astro means space!
Sheldon: Astro means star.
Raj: Okay, let me just tell you, if we were having this argument in my native language, I'd be kicking your butt!
Sheldon: English is your native language!

Sheldon: Yes, since their relationship became carnal, Penny has updated his designated term of endearment, distinguishing him from those she calls "sweetie," usually as an attempt to soften a thinly-veiled insult.
Penny: You're boring people, sweetie.
Sheldon: Although sometimes, she omits the veil entirely.

Leonard: I've always been a little confused abut this -- why don't Hindus eat beef?
Raj: We believe cows are gods.
Sheldon: Not technically. In Hinduism cattle are thought to be like gods.
Raj: Do not tell me about my own culture Sheldon! In the mood I'm in I'll take you out, I swear to cow!

Interesting. Sex works even better than chocolate to modify behavior. I wonder if anyone else has stumbled onto that

Sheldon: Leonard, you can't train my girlfriend like a lab rat
Leonard: Actually, it turns out I can
Sheldon: Well you shouldn't

Penny: I give up, he's impossible
Sheldon: I can't be impossible, I exist. I believe what you meant to say is, "I give up, he's improbable."

Penny: I'll tell you what, next french toast day, I'll make you oatmeal
Sheldon: Good lord, are you still gonna be here next french toast day?

Raj: I don't like bugs, okay? They freak me out.
Sheldon: Interesting. You're afraid of insects and women. Ladybugs must render you catatonic.

Raj: What happened?
Sheldon: Obviously another carnal fiasco with the 'Shiksee' goddess.
Howard: Shiksa. Shik-Sa.
Sheldon: Forgive me. Yiddish was not spoken in East Texas. And if it was, it wasn't spoken for long.

Howard, you know me to be a very smart man. Don't you think that if I were wrong, I'd know it?

Penny: You know, I do understand what you're going through.
Sheldon: Really? Did you just have the Nobel Prize in Waitressing stolen from you?

Hello, Penny. I realize that you're currently at the mercy of your primitive biological urges, but as you have an entire lifetime of poor decisions ahead of you, may I interrupt this one

TBBT Quotes

Penny: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny, get your own Wi-Fi." No spaces.

It's very simple. Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and, as it always has, rock crushes scissors