Sheldon: Leonard, have you ever wondered why my little toes and lateral incisors are significantly smaller than the average for someone of my size?
Leonard: I wonder a lot of things about you, Sheldon, but not that.

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.

Leonard: [to a "smiling" Sheldon] We're here to see Koothrappali, not kill Batman.

Sheldon: I still don't see why I need a driver's license. Albert Einstein never had a driver's license.
Howard: Yeah, but Albert Einstein didn't make me wet myself at 40 miles an hour.
Penny: Yeah, and I never wanted to kick Albert Einstein in the nuts.

Sheldon: Your check-engine light is on.
Penny: Uh huh.
Sheldon: Typically, that's an indicator to, you know, check your engine.
Penny: It's fine. It's been on for like a month.
Sheldon: Well, actually that would be all the more reason to, you know, check your engine.
Penny: Sheldon, it's fine.
Sheldon: If it were fine, the light wouldn't be on. That's why the manufacturer installed that light, to let you know it's not fine.
Penny: Maybe the light's broken.
Sheldon: Is there a check-the-check-engine-light light?

Sheldon: I'm clearly too evolved for driving.