Howard. You do not have a PhD. Your cologne is an assault on the senses, and you're not available for video games during the Jewish high holidays

Sheldon [on weighing which friends to keep]

What part of an inverse tangent approaching an asymptote don't you understand?

Sheldon

A fear of heights is illogical. A fear of falling, on the other hand, is prudent and evolutionary

Sheldon

Sheldon [looking at the women's book in a bookstore]: "Coping with the Death of a Loved One." My condolences
Woman: Thank you
Sheldon: Family or friend?
Woman: Family
Sheldon: Too bad. If it had been a friend, I'm available to fill the void

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

Wolowitz: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Wolowitz: Once you're fluent, you'll have a billion more people to annoy instead of me

Penny: Leonard isn't the kind of guy I usually go out with.
Sheldon: Leonard isn't the kind of guy anyone usually goes out with

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

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?