Leonard: How'd it go with my mother?
Penny: Uh, you know, it started a little rocky, but I think we got to a good place.
Leonard: Wow. Well done.
Penny: Yeah, and when I dropped her off at the hotel, she even gave me a hug.
Leonard: Did she think you were choking or ...?

Amy: Hey, did you guys know that Sheldon had a best friend growing up named Tam?
Leonard: Was that the imaginary talking koala?
Amy: No. He's a real person who apparently betrayed him.
Leonard: Yeah, so did the koala.

President Siebert: Ah. There's my band of brainiacs. Where's Dr. Cooper?
Leonard: He's tearing the mask off nature to look at the face of God.

Penny: All right, this is making me crazy. Somebody's got to go over there.
Leonard: You got feet and legs, you do it.

Penny: No, it does matter. Okay? You were right. It was Halloween. I was dressed as a cat, you were a hobbit. It was right there on that couch.
Leonard: Why didn't you just say that?
Penny: Because I always hated that was our first kiss. I was drunk, and I was still with Kurt, and I was using you to make myself feel better. I just wanted our first kiss to mean something. That's why I said it was the one on your birthday.
Leonard: I like that. We'll make that our official first kiss.

Leonard: Hang on. Are you feeling insecure? Because that's my thing, and if you take it away, I don't know what I'm bringing to this relationship.

Penny: The pastrami truck moved.
Leonard: That is the danger of a restaurant on wheels.

Howard: Wow. I wonder what that guy could've done to make Sheldon not talk to him for 20 years.
Leonard: I wonder if it'd work a second time.

Penny: You really want me to pick up your mother all by myself?
Leonard: Hmm, I just feel like it would be a good chance for you to bond.
Penny: Or a way for you to avoid her?
Leonard: I don't know what he's putting on those cards, but you are smarter than ever.

Leonard: I never wanted to play the cello. How do you meet girls playing the cello? Hey, you want to come over to my house and listen to me play an instrument that sounds like a suicidal bumblebee?

Sheldon: Did you see that? He just cut the line.
Leonard: He's just joining his friends; it's fine.
Sheldon: No, it's not fine. It is a breach of line etiquette.
Howard: We're near the front of the line. We'll get in either way.
Sheldon: What if every person in front of us let someone cut?
Leonard: We'd still get in.
Sheldon: What if each of those people let someone cut?
Leonard: Still get in.
Sheldon: But then each of those people let someone cut?
Leonard: We'd still get in, but first I'd hit you over the head with his stick chair.

Amy: Now, if you'll excuse me, told Sheldon I was going to the market, so I'm taking some of your stuff. [raids the fridge] I was never here.
Leonard: Sometimes you don't see it 'cause she's next to Sheldon, but she's pretty weird.

Howard: You look like you come with a kickstand.
Raj: You can't make me feel bad.
Howard: Hmm, maybe not. Leonard?
Leonard: So, when the aliens brought you back, they just left the probe in?

Penny: Now, why don't you go wash up, and we'll call you when dinner's ready.
Sheldon: Okay. (Sheldon leaves)
Leonard: (surprised) What did you do? Are you a witch?

Leonard: "How are you with pets?" Well, I did take care of Sheldon for 15 years, and he only bit me twice.