Every family in America has a relative holed up in a garage somewhere huffing paint thinner

Leonard: Penny, say hello to Leo.
Penny: Hi, Leo. How are you feeling?
"Leo": Have you ever woken up in a flea-bag motel, covered in your own vomit, next to a transsexual prostitute?
Penny: No.
"Leo": Then don't ask me how I'm feeling.

Sheldon [knocking on Penny's door]: Penny, Penny, Penny...
[Penny opens the door]
Sheldon: Good morning.
Penny: Do you have any idea what time it is?
Sheldon: Of course I do, my watch is linked to the atomic clock in Boulder, Colorado. It's accurate to one-tenth of a second, but as I'm saying this it occurs to me once again your question may have been rhetorical

Wolowitz: I just checked the house. There's probably 20, 25 people in there.
Leonard: You're kidding!
Penny: Is that all?
Leonard: "All?" In particle physics, 25 is Woodstock.

Penny: So, you know, isn't there maybe some way you and Sheldon could compromise on this whole presentation thing?
Leonard: No. Scientists do not compromise. Our minds are trained to synthesize facts and come to inarguable conclusions. Not to mention Sheldon is bat-crap crazy

Howard, would you like to explain to me why your Facebook page has a photo of me sleeping on your shoulder captioned, "Me and My Girlfriend?"

Leonard [referring to Sheldon singing]: What got into him?
Penny: Oh, just a couple virgin Cuba Libres that turned out to be kinda slutty

Penny [to Raj about Lalita]: No one can make you get married. Why don't you just meet this girl and see what happens?
Raj: Haven't you been listening to me? I cannot talk to women!
Leonard: Um, Raj?
Wolowitz: No, no, let's see how long it takes him

Sheldon: When I was a little boy and got sick, which was most of the time, my mother would read [The Monkey and the Princess] to me. It's about an Indian princess who befriends a monkey who was mocked by all the other monkeys because he was different. For some reason I related to it quite strongly.
Penny: I know the reason.
Leonard: We all know the reason

Penny: I need some guinea pigs.
Sheldon: Okay, there's a lab animal supply company in Reseda you can try. But if your research is going to have human applications, may I suggest white mice? Their brain chemistry is far closer to ours.
Penny: I swear to God, Sheldon, one day I'm going to get the hang of talking to you.
Leonard: His mom's been saying that for years

Raj [drunk]: Where did my life go, Penny?
[everyone is shocked Raj is talking to Penny]
Raj: One day, I'm a carefree bachelor, and the next, I'm married and driving a minivan to pee-wee cricket matches in suburban New Delhi.
Penny: Are you talking to me?
Raj: Is there another Penny here?

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?

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?