Leonard: Hi-lo. Oops. I started to say hi and then I switched to hello in the middle. It came out hi-lo. Duh. Uh, it's nice to meet you. I've read both your books and most of your papers. I'm Leonard, I live here. You're brilliant.
Sheldon: I apologize. He's only an experimental physicist.
Elizabeth: No need to apologize. Some of my best friends are experimental physicists. Well, not my best friends, but I know them. My best friend is a molecular chemist named Wendy. I'm sorry, I'm rambling. Hi-lo.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Howard: Are you planning on kidnapping a woman?
Sheldon: Sarcasm?
Howard: Yes, but mixed with genuine concern.

Howard: I have a two-part question.
Sheldon: Go ahead.
Howard: A: Are you kidding? And B: Seriously, are you freaking kidding me?
Sheldon: A: I rarely kid, and B: when I do kid, you will know it by my use of the word "Bazinga".
Howard: So you're saying the two of you are going to be sleeping in the same bed?
Sheldon: Yes. Bazinga.

Sheldon: Now listen, one of the great minds of the 21st century is about to play host to one of the other great minds of the 21st century. So pay attention. Years from now, my biographer might ask you about this event.
Leonard: Oh, I have so many things to tell your biographer.