Penny: If I do well in sales, I could end up making a lot more money than you.
Leonard: Not a problem. I grew up with a mother who emasculated my father financially and in every other aspect of his life, so really it's what I think love looks like.

Leonard: Just out of curiosity, did he ever have a shot with you?
Stephanie: Are you insane, the guy was wearing an eyepatch.
Leonard: So, then why did you--
Stephanie: He said I could drive a car on Mars!

Leonard: Well, they say at the end of your life, you regret the stuff you didn't do more than the stuff that you did. And, I'm pretty sure Alice is the stuff I want to do.

*Leonard tries to slip a note under Penny's apartment door*
Penny: Hi.
Leonard: Oh.
Penny: What's going on?
Leonard: Um, here's the thing. (Reads from the note.) Penny, just as Oppenheimer came to regret his contributions to the first atomic bomb, so too I regret my participation in what was, at the very least, an error in judgment. The hallmark of the great human experiment is the willingness to recognize one's mistakes. Some mistakes, such as Madame Curie's discovery of Radium turned out to have great scientific potential even though she would later die a slow, painful death from radiation poisoning. Another example, from the field of Ebola research-
Penny: Leonard.
Leonard: Yeah.
Penny: (hugs him) We're okay.

Leonard: You know he can't take a trip like this by himself.
Penny: He's a grown man.
Leonard: No, he looks like a grown man. You've seen Freaky Friday, sometimes little kids end up in big person bodies.

Leslie Winkle: Leonard. Hey, it's been a while.
Leonard: Leslie. I can't remember the last time we talked. So much has changed.
Leslie Winkle: Has it?
Leonard: Yeah, uh, um, Penny and I got married.
Leslie Winkle: Wow, congratulations. You know, actually, I thought you'd be living with Sheldon forever.
Leonard: Yeah, .... Well, don't be a stranger.

Penny: That was such a fun night.
Leonard: Probably 'cause you got to see your man up there rockin' the mic.
Penny: Yeah, yeah. I was a little surprised when you decided to beat-box.
Leonard: Oh, that was really an asthma attack. I just sold it.

Sheldon: Here's a fun Postal fact. Yeah, the inner side of our mailbox is under federal jurisdiction. So, if you broke my right thumb, that's Pasadena city police. But if you broke my left thumb, that's the FBI.
Leonard: If I'm going to jail, I'm killing him, not breaking his thumb.

Leonard: Hey, if you're hungry, there's a breakfast buffet at the strip club next door.
Penny: Thanks, but I don't like glitter on my scrambled eggs.
Leonard: I don't think the strippers prepare the meal, but okay.

Penny: You're a big cry baby. You start, I'll join in.
Leonard: I am not a cry baby.
Penny: Toy Story 3.
Leonard: The toys were holding hands in a furnace!

Sheldon: Forgive me for eavesdropping, but as I see it there's a simple solution.
Leonard: Wake up! Wake up! Wake up!

Leonard: Please be good, please be good. Uh-huh, uh-huh. Okay, she writes like she cooks.

Leonard: Ethyl alcohol inhibits electrical conduction in the nerve cells and stimulates re-uptake receptors of inhibitory neurotransmitters like gamma-amino butyric acid.

Leonard: Lobster traps?
Sheldon: Yes. That's how Velma and Scooby smuggled Shaggy into the old lighthouse.

Leonard: You shush. I'm happy. I want to talk about it.