Leonard: If I roll down the windows, everything is peachy. If you roll down the windows, you're still not a doctor.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

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.

Leonard: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

Penny: What do you mean new roommate? What happened to Leonard?
Sheldon: The same thing that happened to Homo Erectus. He was replaced by a superior species.
Raj: I'm the new homo in town.

Penny: So that means, you're a doctor, you're a doctor, you're a doctor, you're a doctor and, Howard, you know a lot of doctors.

Penny: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny get your own Wi-Fi"; no spaces.