Leonard: Have you considered telling her your feelings?
Sheldon: Leonard, I'm a physicist, not a hippie.
Leonard: Well let me see if I can explain your situation using physics. What would you be if you were attached to another object by an incline plane, wrapped helicly around an axis.
Sheldon: Screwed.
Leonard: There you go.

Leonard: When we watch Frosty the Snowman, he roots for the sun.
Sheldon: Excuse me, but the sun is essential for all life on earth. Frosty is merely a bit of frozen, supernatural ephemera in a stolen hat. A crime, by the way, for which he is never brought to account.

Leonard: Well, it seems once again you're caught between a rock and a crazy place.
Sheldon: Oh, I hate when that happens.

Leonard: Well, it wasn't my fault.
Sheldon: The implication being that you somehow tripped and fell into her lady parts?

You call that a glowstick? [Pulls out his light saber and turns it on.] That is a glowstick!

Sheldon: How could you not find him?
Leonard: Because he's hard to find. If he was easy to find, the books would be called "There's Waldo."

Raj: The only thing I've learned in the last two hours is that American men love drinking beer, pee too often, and have trouble getting erections.
Leonard: Focus on the game, not the commercials, Raj.
Raj: I'm just saying, maybe if you people cut back on the beer, you could get out of the bathroom and satisfy your women without pharmaceutical help.

Raj: Woh, woh, woh! I don't want to speak to the FBI.
Leonard: Why not?
Raj: I'm brown and I talk funny.

Leonard: What are you doing?
Amy: We're playing doctor. Star Trek style.
Sheldon: I'm in hell, Leonard. Don't stop.

[Sheldon karate chops Leonard in the shoulder]
Leonard: Ow! Why did you do that?
Sheldon: To send a message: she's not for you!
Leonard: What?
Sheldon: Not for you!

Leonard: Why would you buy peppermint schnapps?
Penny: Because I like peppermint, and it's fun to say schnapps!

Leonard: Why do I have to talk to Penny? She's not my girlfriend.
Sheldon: You invited her to lunch four years ago, everything about her is on you: you make it so!

TBBT Quotes

Sheldon: I recently read that during World War Two, Joseph Stalin had a research program to create supersoldiers by having women impregnated by gorillas.
Howard: What a sick use of science.
Raj: Hey, as long as the baby's healthy.
Amy: I wonder if Stalin considered any other animals.
Leonard: Hippos are the deadliest creature. A half-human, half-hippo soldier would be pretty badass.
Howard: Yes, but when they're hungry-hungry, you can stop them with marbles.
Sheldon: Yeah, the correct animal for interspecies supersolider is koala. You would wind up with an army so cute it couldn't be attacked.

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.