Penny: Can I ask you a question?
Sheldon: Given your community college education, I encourage you to ask as many as possible.

Penny: OK. Well, then, there's a couple of things you should probably know.
Sheldon: I have a master's degree and two doctorates. The things I should know, I do know.

Sheldon: Amy pointed out that, between the two of us, our genetic material has the potential of producing the first in a line of intellectually superior, benign overlords to guide humanity to a brighter tomorrow.
Wolowitz: I'm guessing that future historians will condemn us for not taking this opportunity to kill Sheldon.

Apparently, a semi-incestuous Teens for Jesus hoedown didn't count.

You have broad hips and a certain corn-fed vigor. Is your womb available for rental?

At best, it's a modest leap forward from the technology that gave us Country Bear Jamboree.

That's not afternoon. That's prevening.

Sheldon: Hello, Amy Farrah Fowler. I'm sorry to inform you that you've been taken in by unsupportable mathematics designed to prey upon the gullible and the lonely. Additionally, I am being blackmailed with a hidden dirty sock.
Amy: If that was slang, I'm unfamiliar with it. If it was literal, I share your aversion to soiled hosiery.

Wolowitz: Okay, what if I were to tell you, tomorrow at 4:30, you could meet a woman who has been scientifically chosen to be your perfect mate?
Sheldon: I would snort with derision and throw my arms in the air, exhausted by your constant tomfoolery.

Incidentally, one can get beaten up in school simply by referring to oneself as one.

Yes, in 1917 when Albert Einstein established the theoretic foundation for the laser in his paper "Zur Quantentheorie der Strahlung," his fondest hope was that the resultant device be bitchin'.

Sheldon: As a native Texan, I must say that I've never heard the phrase "yee haw" used in quite that context.
Penny: Oh God.
Sheldon: "Oh God." That I've heard on multiple occasions.

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?