He left a boy. He returns a boy-sized hero.

Sheldon: Flattery will not get you this job, Ms Jensen
Ms. Jensen: It's not flattery, if it's the truth.
Sheldon: Oh, well, thank you. Welcome aboard.

Penny: I'm just a blonde monkey to you, aren't I?
Sheldon: You said it, not me.

Call me a romantic. I like to think your Mark Ruffalo is still out there somewhere.

Your desperate need for friendship makes you weak.

Sheldon: Penny? Please don't hurt my friend.
Penny: That is the last thing I want to do.
Sheldon: Thank you.

Leonard: The guy who seems like an emotionless robot ... is you, but your relationship with Amy is causing you to transform into a red-blooded man with sexual desires.
Sheldon: That is literally the stupidest thing I've heard.

Sheldon: Wolowitz when to MIT. What's your educational background?
Stuart: I went to art school.
Sheldon: Equally ridiculous. Let's go.

Boldly go, Howard Wolowitz.

Would you like some aloe vera? You just got burned.

Sheldon: I'll do it provided I can perform the service in Klingon.
Bernadette: No.
Sheldon: What do you see in her?

Sheldon: He asked her during coitus.
Howard: Did he get down on one knee or were you already there?

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?