Leonard: No, absolutely not.
Sheldon: It's not a big deal.We have latex gloves.
Leonard: I don't care what the symptoms are. My girlfriend is not going to give you a prostate exam.

Stephanie: I don't see anything at all, Sheldon.
Sheldon: Well, you're the doctor, but I am constantly hearing this annoying sound.
Leonard: Me too.
Sheldon: Is it a high frequency whistle?
Leonard: No, it's more of a relentless, narcissistic drone.

Sheldon: *knock knock knock* Leonard? (x3)
Leonard: What, Sheldon!? What, Sheldon!? What, Sheldon!?
Sheldon: Tell me what you see here.
Leonard: The blunt instrument that will be the focus of my murder trial?

Sheldon: I often forget other people have limitations. It's so sad.
Howard: He can feel sadness?
Leonard: Not really. It's what you and I would call condescension.

Mary Cooper: You know, you two make a cute couple.
Leonard: No, no we're not, we're not a couple, we're single, two singles, like those individually wrapped slices of cheese that are friends.
Mary Cooper: Did I pluck a nerve there?
Howard: Oh yeah.

Leonard: I love cheesecake.
Sheldon: You're lactose-intolerant.
Leonard: I don't eat it. I just think it's a good idea.

Leonard: That's right, you saw what you saw. That's how we roll in the Shire!

Penny: I need some guinea pigs.
Sheldon: Okay, there's a lab animal supply company in Reseda you can try. But if your research is going to have human applications, may I suggest white mice? Their brain chemistry is far closer to ours.
Penny: I swear to God, Sheldon, one day I'm going to get the hang of talking to you.
Leonard: His mom's been saying that for years.

Leonard: Homo habilis discovering his opposable thumbs says what?
Kurt: What?

Penny: Why can't all guys be like you?
Leonard: Because if all guys were like me the human race couldn't survive.

Wolowitz: So, how'd it go with Leslie?
Leonard: Oh, we tried kissing, but the earth didn't move. I mean any more than the 383 miles it was gonna move anyway.

Sheldon: I couldn't sleep knowing that just outside my bedroom is our living room and just outside our living room is that hallway and immediately adjacent to that hallway is [Penny's messed up apartment]!
Leonard: Do you realize if Penny wakes up there's no reasonable explanation to why we are here?
Sheldon: I just gave you a reasonable explanation.
Leonard: No, no. You gave me an explanation. Its reasonableness will be determined by a jury of your peers.