Leonard: Um, I picked it. You're the one who told me to stop being such a satisficer all the time.
Sheldon: What? I did not. I just pointed out that you were one. It's what I like best about you. Well, that and those little notes you leave in my lunch.
Amy: I leave those!
Sheldon: Well, that's disappointing. I already know that you heart me. Now I don't know if Leonard does.

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.

Amy: Wow. Déjà vu.
Sheldon: Amy, you're a neuroscientist. you know the latest research into déjà vu suggests it's nothing but the frontal regions of the brain attempting to correct an inaccurate memory.
Amy: You telling me stuff I already know is definitely déjà vu.

Sheldon: How can I tell if I'm doing something for a noble reason or a selfish reason?
Amy: Try saying the thing in your head and see if you can add the words, "That'll show 'em."

Sheldon: Leonard's about to demand a job that I don't think the university will give him. I'm worried he's making a giant mistake. But maybe I only think that because deep down I don't want him to succeed.
Amy: The fact that you're worried about your motivation supports the idea that you genuinely care for your friend.
Sheldon: I do. Thank you, Amy. You know what? After I've talked to Leonard, you've earned yourself a bonus lecture on Sponge Hulk.
Amy: That'll show me.