Sheldon: Look at Planck's Constant. People say it's arbitrary. It could not be less arbitrary. If it varied even slightly, life as we know it would not exist. Bam! Now, let's reconsider the entire argument, but with entropy reversed and effect preceding cause, so you are thinking of a universe that's not expanding from the center. No, it is retreating from a, from a possibility space. Bam! This is a space where we are all essentially Alice through the Looking Glass, standing in front the Red Queen, and we're being offered a cracker to quench our thirst. Bam! Of course, in another universe, let's call it universe prime, there's another Sheldon. Let's call him Sheldon prime...
Penny: We should have let him go to bed.
Leonard: Bam.

Penny: Come on. What about the living organism of the workforce and the American spirit and Jiminy Crockett at the Alamo?
Leonard: Davy Crockett. Jiminy Crockett was a cricket.

Penny: Okay, I'll go. Howard and Bernadette, I know you two planned on getting married in a big fancy wedding, but when you're in love, it doesn't matter where or how these things happen. It just matters that you have each other.
Leonard: Hmm.
Penny: Problem?
Leonard: No.
Sheldon: I think the Reverend Hofstadter is making an ironic connection between your statement about love and your rejection of his proposal in the bedroom.
Penny: Oh, grow up.

Raj: Oh, boy, Sheldon's going to freak out.
Leonard: Yeah, he worships Hawking.
Howard: I was actually thinking about bringing him along when I go over there so he can meet the great man.
Raj: That's really nice of you, Howard.
Howard: Hmm, it's no big deal.
Leonard: Boy, a restraining order from Stephen Hawking. It'll look so nice next to the ones he's already got from Leonard Nimoy, Carl Sagan and Stan Lee.

Leonard: Look, Sheldon, I know its in the agreement, and if you turn into a zombie, I promise I will not kill you. In fact, Ill even let you eat my brains. But I am taking Penny to Switzerland.

*Penny sneezes*
Leonard: Gesundheit. Or as they say in Switzerland, gesundheit. You getting a cold?
Penny: No, no, it's probably just allergies.
Leonard: Do you want an allergy pill? 'cause I have 'em all. Prescription, nonprescription, foreign, domestic, experimental.
Penny: Do any of them work?
Leonard: Not really. I'm just an enthusiast.

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.

Sheldon: I must say, I'm shocked by this betrayal.
Leonard: I didn't betray Penny.
Sheldon: Not Penny, me!
Leonard: How am I betraying you?
Sheldon: Elizabeth's my friend, and you're playing with her!
Leonard: Yeah, I guess I did.

Sheldon: I'll save you the pain and nervousness of waiting for the answer. I agree to be part of your project. Congratulations.
Leonard: Oh, yay for me.

Leonard: We're not wasting time with names right now.
Sheldon: I see. Is that decision open for discussion?
Leonard: No.
Sheldon: Is the decision to not discuss it open for discussion?
Leonard: No.

Penny: Hi. I'm sorry to bother you guys, but you've got to come take your Sheldon back.
Leonard: What's he doing in your apartment?
Penny: Well, he was moping down in the lobby, so I invited him over and now I regret it.
Leonard: Why do you regret - Uh, never mind, stupid question.

Priya: How many Star Trek uniforms do you have?
Leonard: Just two. Everyday and dress.

Priya: You need to cut the cord with Penny.
Leonard: Oh. Okay.
Priya: You don't sound very confident.
Leonard: No, no, I'm confident. It's not like I'm unfamiliar with the get lost conversation. Although, this will be the first time Illl be the one saying it.

Leonard: Oh, hi.
Penny: Hey, you. What happened with the contacts?
Leonard: One of them's upstairs. The other one sort of slipped back into my skull.

Priya: So did you get to talk to Penny?
Leonard: Oh, yes. Indeed, I did.
Priya: And?
Leonard: She completely understood everything I said. Case closed.
Priya: Was she upset?
Leonard: Maybe, but that's not my problem. She's not my girlfriend, you are.
Priya: I hope you weren't cruel to her.
Leonard: Is the autumn cruel for letting the flowers die, or is that just nature's way?