Alicia: Cool t-shirt.
Penny: Oh, yeah, I don't usually dress like this. I'm going jogging.
Sheldon: You don't jog.
Penny: I can start.
Sheldon: True, but the more likely explanation for your attire is that you're out of clean clothes again.
Penny: Thank you, Sheldon.
Sheldon: You're welcome, Penny.

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: Penny, let me take this opportunity to point out that you are looking particularly ravishing today.
Penny: Not with a thousand condoms, Howard.
Wolowitz: So there is a number.

Penny: Leonard, and Howard, and Raj, they aren't like other guys. They're special.
Alicia: Okay, they're special, and?
Penny: Well let's see how can I explain this. Um. They don't know how to use their shields.
Alicia: Shields?
Penny: Yeah. You know like in Star Trek and you're in battle, and you raise the shields.
*Realizing what she said* Where the hell did that come from?

Howard: Enough with the guilt, ma. We'll still see each other. I'll come over every night and have dinner with you.
Mrs. Wolowitz The hell you will! What am I running here, a fancy restaurant? Does this look like the Olive Garden?