Sheldon: You know, I try very hard to make our lunch hours educational and informative, but your insistence on talking about your own lives stymies me at every turn.
Leonard: Fine, Sheldon, tell us about your giant rodents.
Sheldon: No, you squandered your time with me, and the moment has now passed. Feast on your disappointment, much as the capybara feasts on its own waste.

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.

Wolowitz: But you love that spot.
Sheldon: No, I love my mother. My feelings for my spot are much greater.

Penny: OK Sheldon, what can I get ya?
Sheldon: Alcohol.
Penny: Could you be a little more specific?
Sheldon: Ethyl alcohol, 40 millilitres.

Penny: Sheldon, you can't re-program people.
Sheldon: No, you can't re-program people.