Sheldon: Looking out at your fresh young faces, I remember when I, too, was deciding my academic future as a lowly graduate student. Of course, I was fourteen. And I had already achieved more than most of you could ever hope to, despite my 9:00 bedtime. Now, there may be one or two of you in this room who has what it takes to succeed in theoretical physics, although it's more likely that you'll spend your scientific careers teaching fifth graders how to make papier-mâché volcanoes with baking soda lava.
Leonard: Oh, good God.
Sheldon: In short, anyone who told you that you would someday be able to make some significant contribution to physics, played a cruel trick on you—a cruel trick indeed. Any questions? ... Of course not. I weep for the future of science

Rajesh: Isn't there a University policy against dating graduate students?
Leonard: No. If you can talk to them, you can ask them out.
Rajesh: Damn, there's always a catch

Sheldon: Please, please, I don't have a lot of time. Ramona finally dozed off and I need you to help me get rid of her.
Penny: Get rid of her how?
Sheldon: I don't know, but apparently I'm in some kind of relationship, and you seem to be an expert at ending them.
Penny: Excuse me?
Sheldon: I see man after man leaving this apartment, never to return.

Sheldon: How am I going to get to work?
Leonard: Take the bus.
Sheldon: Oh, I can't take the bus anymore. They don't have seatbelts, and they won't
let you lash yourself to the seat with bungee cords.
Leonard: You tried to lash yourself to the seat with bungee cords?
Sheldon: I didn't try; I succeeded.

Sheldon: Leonard, have you ever wondered why my little toes and lateral incisors are significantly smaller than the average for someone of my size?
Leonard: I wonder a lot of things about you Sheldon, but not that

They gave him an assistant? If I want a new pen I have to go to the bank with wire cutters

Wolowitz [about Raj]

Raj: Did you see my limo downstairs?
Leonard: Yeah.
Raj: It's bigger than the house my grandfather grew up in.
Leonard: Great.
Raj: It has more food, too

Leonard: It wouldn't kill us to meet new people.
Sheldon: For the record, it could kill us to meet new people

Wolowitz: So you're just going to sit around here and mope while Penny is out with Dr. Apu from the Kwik-E-Mart?
Leonard: It's not a date, and that's racist.
Wolowitz: It can't be racist, he's a beloved character on The Simpsons

Leonard: If we do get a new friend, he should be a guy you can trust. You know, a guy who has your back.
Wolowitz: And he should have a lot of money and live in a cool place down by the beach where we could throw parties.
Sheldon: And he should share our love of technology.
Wolowitz: And he should know a lot of women.
Leonard: Okay, let's see: money, women, technology. Okay, we're agreed. Our new friend is going to be Iron Man

Boy, you'd think you could trust a horde of Hungarian barbarians

Penny

Penny: What's AFK?
Sheldon: Away From Keyboard.
Penny: Oh, I see.
Sheldon: What does that stand for?

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?