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.

Howard: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Howard: Once you're fluent, you'll have a billion more people to annoy instead of me.

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.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: Really? You're going to risk getting sleepy in the middle of your themodynamic fluctuations seminar? You know what happens when you yawn in public.
Sheldon: Everyone will see my oddly shaped uvula.

Bernadette: Sheldon, when was the last time you got any sleep?
Sheldon: I don't know. 2 or 3 days. Not important. I don't need sleep, I need answers. I need to determine where in this swamp of unbalanced formulas squatteth the toad of truth.
Penny: Toad of truth? Is that a physics thing?
Leonard: No, that's a crazy thing.

Leonard: How was Nebraska?
Penny: Oh, better than North Dakota! I guess that joke's only funny in Nebraska.
Sheldon: From the data at hand you really can't draw that conclusion. All you can say with absolute certainty is that that joke is not funny here.
Penny: Boy, it's good to be back.