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!

Sheldon: My brain is better than everybody's!