Leonard: I'm done enabling him. Like, this is his spot and-and the thermostat has to be set to his comfort level, even though he doesn't even live here anymore and I'm always chilly.
Raj: Is that why you wear a hoodie all the time?
Leonard: Why would-- Yes! To accommodate Sheldon! And what-what about this-this thing? Why is it here? I'll tell you why. Because it was here when I moved in, and, for no earthly reason, he forbade me to touch it.
Amy: Well, if you don't like it, get rid of it. Put it in the closet.
Leonard: You know what, I will. [Leonard tries to move the helix structure. Lots of little beads fall off and come crashing to the floor]
Raj: I bet that's the reason.

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

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.

Professor Proton: Can I ask you a question?
Leonard: Yeah, sure.
Professor Proton: Why do you put up with Sheldon?
Leonard: Oh, you know because we're friends.
Professor Proton: Why?
Leonard: Wow, you ask really hard questions. Look, I know he can be aggravating, but what you have to remember is he's not doing it on purpose, it's just how he is. But he's also loyal and trustworthy and we have fun together.
Professor Proton: You know you're describing a dog?
Leonard: He did bite me once. But in his defense, I came up behind him while he was eating.
Professor Proton: They hate that.
Leonard: Sheldon is the smartest person I have met. He's a little broken and he needs me. And I guess I need him too.
Professor Proton: Why is that?
Leonard: Boy, you will not let this go, will you?

Amy: Oh. That's me. Hello? Yes, this is Dr. Fowler. I see. Okay, thank you. We won.
Penny: Congratulations!
Leonard: Oh, my God!
Sheldon: We did it.
Amy: I know. Can you believe it?
Sheldon: That's a good point. What if I'm dreaming? [Leonard slaps Sheldon] We won the Nobel Prize!

Penny: So, I guess the only thing that actually stays the same is that things are always changing.
Sheldon: Interesting. So you're saying the inevitability of change might be a universal constant.
Penny: Well, there's a little more to it than that, but, yeah, sure.

Penny: Well should we wake him up?
Leonard: Well, he did say if he fell asleep, we were allowed to slap him awake.
Penny: Oh, boy.
Leonard: Wait a minute. Why do you get to do it?
Penny: 'Cause I called it.
Leonard: Well, you can't just call it. You have to earn it.
Penny: Oh, and you've earned it?
Leonard: No one has earned it more than me. [Amy clears her throat] You have your whole life to smack him around. This is my time.