Sheldon: I need to sleep here tonight.
Raj: Why?
Sheldon: Howard is a total ass, Bernadette is in Penny's bed, Amy bites and Penny may or may not have coitus with Leonard.
Raj: Okay, come in.

Sheldon: Well, I enjoyed that more than I thought I would.
Amy: Me too!
Sheldon: I look forward to your next birthday when we do it again!
Amy: That works for me.

Penny: I always tear up when the Grinch's heart grows three sizes.
Sheldon: Tears seem appropriate. Enlargement of the heart muscle, or hypertrophic cardiomyopathy, is a serious disease which can lead to congestive heart failure.

Leonard: Wow, Donkey Kong. This was my game when I was a kid.
Sheldon: Because it's a story of a pretty blonde girl tirelessly pursued by a small oddly-shaped man?

Sheldon: You may have gone to Cambridge but I'm an honorary graduate of Starfleet Academy.

Sheldon: I made a new friend who likes trains as much as I do, I kissed Amy on the lips, and the conductor played his banjo for me.

Sheldon: There's no need to interact with me. I'm just here to observe.

Sheldon: I'm not saying that all senior citizens that can't master technology should be publicly flogged. But, if we made an example of one or two it might give the others incentive to try harder.

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

Amy: Acquiring a joint pet is a big step for us.
Sheldon: It's true. It means we care so much about each other, there's enough left over for an eight-ounce reptile.

Amy: Did you hold the baby?
Sheldon: I did.
Amy: And how did it make you feel?
Sheldon: Looking into the blank, innocent eyes of a creature that couldn't begin to comprehend anything I was saying ... basically another day at the office.

Amy: It's sweet that you care about him so much.
Sheldon: I do. And I wouldn't be able to forgive myself if something happened to him, and I wasn't at his bedside to say "I told you so".

Penny: Well, what's the third option?
Sheldon: That I have coitus with her.
(Penny's wine glass smashes in her hand)

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.

Sheldon: Doctor Greene, question?
Dr. Greene: Yes?
Sheldon: You've dedicated your life's work to educate the general populous about complex scientific ideas.
Dr. Greene: Yes, in part.
Sheldon: Have you ever considered trying to do something useful? Perhaps reading to the elderly?
Dr. Greene: Excuse me?
Sheldon: Yeah, but not your books. Something they might enjoy. I kid of course, big fan.