Leonard: (On the phone) I'm really very busy. Is there any way that we can put this off until I have more time to prepare? ... Of course. But, uh, you understand my trepidation.
Penny: What's that about?
Howard: Not a clue.
Leonard: Can't we just postpone it till the spring? Maybe next summer?
Sheldon: This should be fairly easy to deduce. He's holding the phone to his left ear. Ears do not cross hemispheres, so he's using the analytical rather than the emotional side of the brain, suggesting that he has no personal relationship with the caller.
Leonard: No, I didn't realize it had been so long. Sure, I guess there's no other choice but to just go ahead and do it.
Sheldon: He's referring to an activity he has done before. It's unpleasant and needs to be repeated. This suggests some sort of invasive medical test, like perhaps a colonoscopy.

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.

Beverly Hofstadter: It might explain why the two of you have created an ersatz homosexual marriage to satisfy your need for intimacy.
Howard: Say what?

Leonard: She's only been here a day and a half, and I'm seriously considering alcoholism as a new career path.
Penny: Hey, I talked to her for five minutes yesterday, and I've been half bombed ever since.

Penny: I'm curious. What was Leonard like when he was little?
Beverly Hofstadter: I think you mean young. He's always been little.