Leonard: I think I'm starting to get this.
Rajesh: Really? The only thing I've learnt in the last 2 hours is that American men drink a lot of beer, pee too often and have trouble getting erections.
Leonard: Focus on the game, not the commercials Raj.

Leonard: When we watch Frosty the Snowman, he roots for the sun.
Sheldon: Excuse me, but the sun is essential for all life on earth. Frosty is merely a bit of frozen, supernatural ephemera in a stolen hat. A crime, by the way, for which he is never brought to account.

Girl: What are you gonna get, Raj?
Raj: With my luck, hepatitis.

Wolowitz: Well no, you're mistaken. You give speeches all the time. What you can't do is shut up.

Sheldon: I am the ball, my thoughts are its thoughts, its holes are my holes.

Howard: Sheldon knows football? I mean Quidditch, sure, but football?

Howard: Hope you don't mind, I told my girlfriend, Bernadette, she can join us for dinner.
Leonard: Sure, the more the merrier.
Sheldon: Wait, no. That's a false equivalency. More does not equal merry. If there was 2000 people in this apartment right now, would we be celebrating? No, we'd be suffocating.

Sheldon: I assure you, you'll be sorry that you wasted your money on an iPod when Microsoft comes out with theirs.
Rajesh: Do you have an opinion about everything?
Sheldon: Yes.
Howard: And you just assume you're right?
Sheldon: It's not an assumption.

Penny: Don't you dare knock!

Sheldon: You can't make a half sandwich. If it's not half of a whole sandwich, it's just a small sandwich.

Leonard: Okay, I know what you're doing.
Sheldon: Really?
Leonard: Yes, you're using chocolates as positive reinforcement for what you consider correct behavior.
Sheldon: Very good. Chocolate?
Leonard: No, I don't want any chocolate! Sheldon, you can't train my girlfriend like a lab rat.
Sheldon: Actually, it turns out I can.

Leonard: They're gonna get beaten up at that club.
Penny: They're gonna get beaten up at Walgreens.

Sheldon: Hello, Penny. I realize you are currently in the mercy of your primitive biological urges. But, as you have an entire lifetime of poor decisions ahead of you, may I interrupt this one?

Sheldon: Leonard, when that woman moved in three years ago I told you not to talk to her, and now look. We're going to be late for the movies.

Sheldon: But evolution is not opinion, it's a fact.
Mary Cooper: And that is your opinion.
Sheldon: [to Leonard, Howard and Raj] I forgive you, let's go home.