Sheldon: (to Leonard, who has decided to give up on Penny) Well, at least now you can retrieve the black box from the twisted, smoldering wreckage that was once your fantasy of dating her and analyze the data so you don't crash into Geek Mountain again.

Sheldon: And to think, I was about to waste the last of my good haemorrhoid cream on you.

Sheldon: I'd like to say I'm very happy that you're back together. And if I can figure out a way to do so and sound sincere, I will.

Sheldon: As a mental exercise, I invite you to figure out why the two of us can't play three-person chess.

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.

Leonard: I don't think I can go to the North Pole.
Sheldon: OK, Leonard, I know you're concerned about disappointing me, but I want you to take comfort from the knowledge that my expectations of you are very low.

Sheldon: Why does everyone suddenly wanna talk to me alone? Usually nobody wants to be alone with me.

Sheldon: Oh Amy, I've never been touched like this before.

Sheldon: I couldn't sleep knowing that just outside my bedroom is our living room and just outside our living room is that hallway and immediately adjacent to that hallway is this!
Leonard: Do you realize if Penny wakes up there's no reasonable explanation to why we are here?
Sheldon: I just gave you a reasonable explanation.
Leonard: No, no. You gave me an explanation. Its reasonableness will be determined by a jury of your peers.
Sheldon: Don't be silly. I have no peers.

Leonard: I don't have a problem with Stuart. Besides, he gives us a 20% discount at his comic book store.
Sheldon: Well, I don't sell my friendship that cheaply.
Stuart: I can go 30.
Sheldon: Welcome aboard, old chum.

Sheldon: *Knocks Knock Knock* Empty room (x3). If somebody answers, I'm going to freak out.

Amy: How did you get into my apartment?
Sheldon: Wow. Is that the kind of nagging I can expect now that you're my girlfriend?

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

Leonard: You are not Isaac Newton.
Sheldon: No, no, that's true. Gravity would have been apparent to me without the apple.

Sheldon: People of Sheldonopolis, this is your mayor. Follow me. If the children can’t run, leave them behind. Oh, the simulated horror!