Leonard: Oh, who am I kidding? I can't go through with this, you need to call her and cancel.
Sheldon: Me?
Leonard: Yes.
Sheldon: What should I tell her?
Leonard: I don't know. Tell her I'm sick.
Sheldon: Okay.
Leonard: Not the kind of illness that will make her want to come over and take care of me, but nothing so critical that she'll feel uncomfortable going out with me in the future if I want to try this again.
Sheldon: Got it. So I'm assuming nothing venereal. I'll just tell her that you had a routine colonoscopy and haven't quite bounced back.

Raj: I don't like bugs, okay. They freak me out.
Sheldon: Interesting. You're afraid of insects and women. Ladybugs must render you catatonic.

Sheldon: Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and as it always has, rock crushes scissors.

Sheldon: Why are you crying?
Penny: Because I'm stupid.
Sheldon: That's no reason to cry. One cries because one is sad. For example, I cry because others are stupid, and that makes me sad.

Sheldon: I think that you have as much of a chance of having a sexual relationship with Penny as the Hubble telescope does of discovering at the center of every black hole is a little man with a flashlight searching for a circuit breaker.

Howard: Sheldon, if you were a robot and I knew and you didn't, would you want me to tell you?
Sheldon: That depends. When I learn that I'm a robot, will I be able to handle it?
Howard: Maybe, although the history of science fiction is not on your side.

Wolowitz: Love is not a sprint, it's a marathon, a relentless pursuit that only ends when she falls into your arms - or hits you with the pepper spray.