Leonard: Hey, did you ever think about the military applications for the guidance system?
Sheldon: Of course.
Leonard: Does it bother you?
Sheldon: No, it did at first. But then I talked it through with Frank and Alicia, and they really helped put things into perspective.
Leonard: Who are these people?
Sheldon: Leonard, friends are like toilet paper. It's good to have extras under the sink.

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: Well, it makes perfect sense. Because you're an expectant mother, you can't drink alcohol. I don't like to. You can't have sushi. I don't like to. You can't go in hot tubs. I consider them vats of sweaty people soup.
Bernadette: Gee, Sheldon, I dont know.
Sheldon: Oh, come on. Roller coasters, caffeine, runny eggs, I've been avoiding these things all my life. And now, because you're pregnant, you have to.

Raj: Hey, dude, you're killing me with Claire.
Zack: What are you talking about?
Raj: I mean, come on, look at you. You're classically handsome, you've got a swimmer's body. Next to you, I look like me.

Raj: Yeah, okay, just do me a favor and stop talking about how great Claire is.
Zack: Anything for you, my little foreign friend.