Sheldon: You know, the German philosopher Friedrich Nietzsche believed that morality is just a fiction used by the herd of inferior human beings to hold back the few superior men.
Leonard: Thanks, that actually does help.
Sheldon: It's worth noting that he died of syphilis.

Sheldon: "See you in hell Sheldon"? The most frightening thing about that is the missing comma.

Sheldon: Come on out, merry pranksters. Take a bow!

Leonard: You may be from Texas, but I'm from New Jersey.

(Leonard & Alice are kissing)
Leonard: Damn it, I can't. I can't do this.
Alice: Is it my tongue stud? 'Cause if that freaks you out, you're in for a real surprise later on.

Leonard: Well, they say at the end of your life, you regret the stuff you didn't do more than the stuff that you did. And, I'm pretty sure Alice is the stuff I want to do.

Leonard: Oh. Watch out, Sheldon. This little boy Casper is a g-g-g-ghost!
Sheldon: Droll.
Howard: Not as droll as a grown man passed out in a puddle of his own urine.
Leonard: That was pretty droll. With a hint of ammonia.

Penny: Leonard, you're looking for a way to sleep with both women and have everybody be happy about it.
Leonard: Now we're getting somewhere.
Penny: What does your gut tell you?
Leonard: Go ask Penny; she'll know what to do.

Howard: You should've seen the look on your face!
Sheldon: Oh, yes. The slightly widened eyes of mildly startled.

Sheldon: And reverse the spin on the anti-proton, and gamma becomes alpha multiplied by a matrix of I comma zero. And there we have it, conclusive proof that I am absolutely useless after nine o'clock.

(After Sheldon passes out after the Halloween prank)
Howard: who had there money on faint?
Raj: I had pee his pants.
Leonard: Hang on, looks like everyone's a winner.

Leonard: You see, I used to be a jackass, but I stopped myself. I became a good guy. See, that's kind of my superpower. I'm like Captain Good Guy!
(Alice pushes him out, then slams door)
Leonard: It's okay. Did the right thing. *tightens his jacket* You idiot!

Leonard: You're talking like a crazy person.
Mary: Actually, I had him tested as a child. Doctor says he's fine.
Sheldon: Told ya.
Mary Cooper: Although, I do regret not following up with that specialist in Houston.

Sheldon: You can lead a chicken to crisco, but you can't make your mother fry it.

Raj: I couldn't find you guys, so I bought six new friends! Sadly, three of them are dead.