Leonard: Well, Penny can be very persuasive. She's gotten me to do a lot of things I wouldn't normally do.
Amy: Because she has sex with you.
Leonard: Yeah, she does.

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: 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.

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

Penny: Sheldon, what did we say about being a nicer friend?
Leonard: Thank you.
Penny: Leonard, what did we say about being a gullible weeny?

Raj: Hey, listen to this. Murder, cannibalism and satanic rituals are just a few of the thousand-plus horrors that await.
Howard: I just helped my mum out of the tub, so I'm one slippery horror ahead of you.

Raj: You know when Cinnamon won't take her medicine. I hide it in a piece of cheese.
Howard: Good idea. We can wrap up the pill in cheese, feed it to Cinnamon and then my mom can eat Cinnamon.