Sheldon: What? No knock? What's the fracas?

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 looking over my text correspondence with Beverly and I don't see anything that would have given her offense. Nothing's ambiguous, I spell everything out. Including "laugh out loud" and "what's the fracas?"

Amy: Are you really not gonna pick up your mother?
Leonard: No. It's fine, she likes to take a cab or a shuttle. That way she can meet people.
Amy: Well, that's kind of nice.
Leonard: Yeah, she always says that a stranger is just a person whose emotional weak point you haven't found yet.
Sheldon: Your mom is the best.

Leonard: How was your flight?
Beverly Hofstadter: There were some parents with a baby. A lot of crying.
Leonard: Well, babies do that.
Beverly Hofstadter: No, it was the parents. It seems they couldn't handle some constructive criticism.