Sheldon: All right, are you familiar with the development that resulted from Honore Blanc's 1778 use of interchangeable parts? The assembly line, of course.
Penny: Okay, you know what, if I'm not allowed to be snide, you're not allowed to be condescending.
Sheldon: That wasn't a part of our original agreement, and I do not agree to it now.
Penny: All right, fine. How are we supposed to set up machines and conveyor belts in my apartment?
Sheldon: You're thinking of the moving assembly line, an understandable but not excusable mistake. No, the moving assembly line, that was introduced by Henry Ford in 1908. That innovation is what made possible our modern consumer culture by enabling a low-unit cost for manufactured goods. I guess that isn't one of the topics discussed on your Radiohead.

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'm sorry, coffee's out of the question. When I moved to California I promised my mother that I wouldn't start doing drugs.

Sheldon: You are effectively paying yourself five dollars and nineteen cents a day.
Penny: A day?
Sheldon: There are children working in sneaker factories in Indonesia who out-earn you.

Sheldon: Camouflaging bald spots. That's primarily a male concern. Perhaps we could expand our market.
Penny: How are flower barrettes going to appeal to men?
Wolowitz: We add Bluetooth.