Leonard: What makes you think she wouldn't have sex with me? I'm a male and she's a female.
Sheldon: Yes, but not of the same species.

Sheldon: (Knocking at Penny's door) Penny! Penny! Penny! Penny! Penny! Penny! Penny! Penny! Penny! Penny! Penny! Penny!
Penny: What the hell is wrong with you?
Sheldon: I'm the Flash, I just knocked 30 thousand times.

Sheldon: I recently had a dream that I was a giant. But everything around me was to scale so it all looked normal.
Leonard: Well, how did you know you were a giant if everything was to scale?
Sheldon: I was wearing size a million pants.

Sheldon: What are the sleeping arrangements? We've only been dating for three years. If we were to share a room people might talk.

*After getting a spare in the bowling match*
Sheldon: Thank you, Jesus! As my mother would say.

Sheldon: Proxima Centauri's the nearest star. The celestial bodies that follow are:
Alpha Centauri A, Toli, Barnard's Star, Wolf 359, Laland 21185, Sirius A, Sirius B, BL Ceti, UV Ceti, Ross 154, Ross 248, Epsilon Eridani, Lac 9352, Ross 128, EZ Aquarii A, EZ Aquarii B, EZ Aquarii C, Procyon A.
Those are the stars that are nearest to me,
Tra la la and fiddle dee dee.

Penny: Would it be weird if I used your shower?
Leonard: No.
Sheldon: Yes.
Leonard: (to Sheldon) No!
Sheldon: No?
Leonard: No!
Sheldon: (to Penny) No.

Sheldon: Oh, what fresh hell is this?
Biosuit Nurse: Wait, you can't leave here, you've been exposed.
Sheldon: (Covering his face with his shirt) No, I haven't. It's all good.

Sheldon: The word is Polish. See, look.
Polish sausage. And the model of the solar system developed by Nicolaus Copernicus, a Polish astronomer. And then, finally, if that wasn't enough, which it should've been, this is Madame Curie killing herself by discovering radium, who, although she was a naturalized French citizen, was Polish by birth.
Penny: Excuse me, the word is polish. See? Small p.
Sheldon: Ah! So it is. I guess we both share blame on this one.

Leonard: Have you considered telling her how you feel?
Sheldon: Leonard, I'm a physicist, not a hippie.

Sheldon: You know, I'm given to understand that there's an entire city in Nevada devoted specifically to help people like Howard forget their problems. They replace them with new problems such as alcoholism, gambling addiction and sexually transmitted diseases.

Leonard: You know what, go to Hell and set their thermostat.
Sheldon: I don't have to go to Hell. At 73 degrees, I'm there already!

Penny: Sheldon, you can't re-program people.
Sheldon: No, you can't re-program people.

Sheldon: Leonard, I don't think I can do this.
Leonard: What are you, kidding? You're a semi-pro.
Sheldon: No, we are committing genetic fraud. There's no guarantee that our sperm's going to generate high-IQ offspring. Think about that. I have a sister with the same basic DNA mix who hostesses at Fuddruckers.

Sheldon: Well, this is different. Candles and music.
Amy: Do you like it?
Sheldon: It's kind of spooky.
Amy: I can change it back.
Sheldon: No, it's your birthday. As long as no one jumps out in a hockey mask, I'll be fine.