Penny: So it's fine with you if I'm not smart.
Leonard: Absolutely. [Penny closes the door on him] Okay, this time I know where I went wrong

Leonard: [Sheldon] says he's moving out.
Raj: What did you do? Did you change the contrast or brightness settings on the television?
Leonard: No.
Raj: Did you take a Band-Aid off in front of him?
Leonard: No.
Wolowitz: Did you buy generic ketchup? Forget to rinse the sink? Talk to him through the bathroom door?

Penny [referring to Sheldon]: What's up with Ichabod?
Leonard: Oh, he's trying to make a new friend
Penny: Well good for him
Leonard: Unless he makes one out of wood like Geppetto, I don't think it's going to happen

Penny: Yes, I will go out with you.
Leonard: Really?
Penny: Yeah. Why not? I mean, what do I have to lose?
Leonard: Yeah. That's the spirit

Leonard: I don't think I can go out with [Penny] tonight.
Sheldon: Then don't.
Leonard: Other people would say, "Why not?"
Sheldon: Other people might be interested

Leonard: Why are you learning Chinese?
Sheldon: I believe the Szechuan Palace has been passing off orange chicken as tangerine chicken, and I intend to confront them.
Leonard: If I were you, I'd be more concerned with what they're passing off as chicken

Leonard: What happened?
Penny: Well, I went over to Mike's to make up with him.
Leonard: Yeah. No, I know that part.
Penny: But he had already moved on.
Leonard: Already? That was quick.
Penny [crying]: That's what I said to the woman who had her legs wrapped around his neck!

Penny: I swear to God, I am done with guys like that. You know, macho with the perfect body and hair, and money.
Leonard: Yeah, that must get old quick

Leonard: Now that I'm actually about to go out with Penny, I'm not excited, I'm nauseous.
Sheldon: Then your meal choice is appropriate. Starch absorbs fluid which reduces the amount of vomit available for violent expulsion

Penny: Maybe we should talk first.
Leonard: Okay, but before you say anything, have you ever heard of Schrödinger's cat?
Penny: Actually, I've heard far too much about Schrödinger's cat.
Leonard: Good.
[Leonard kisses Penny]
Penny: Alright, the cat's alive. Let's go to dinner

Leonard: I'm her friend, I'm not going to take advantage of her vulnerability.
Wolowitz: Wait, so you're saying that if in the depths of despair she throws herself at you and demands you take her right there, right now, you'll just walk away?
Leonard: I said I'm her friend, not her gay friend

Leonard: I don't celebrate my birthday.
Penny: Shut up. Yeah, you do.
Leonard: It's no big deal. It's just the way I was raised. My parents focused on celebrating achievements and being expelled from a birth canal was not considered one of them

TBBT Quotes

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.

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.