Leonard: Well, how about we stop being so scared of losing each other, and just be together?
Penny: That sounds nice.
Leonard: Good. I've loved you from the moment we met and I will keep loving you until the end of time.
Penny: Oh my God, that is the most beautiful thing anyone's ever said to me.
Leonard: Yeah? That's because you're beautiful, and your beauty fills my heart with love and song.
Penny: Getting kind of cheesy, Leonard.
Leonard: You think that's cheesy? Buckle up.
(Leonard gets down on one knee)
Leonard: Penny Hofstadter, will you please stay married to me?
Penny: Oh dammit, you topped it.

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?

Sheldon: Thankfully all the things my girlfriend used to do can be taken care of with my right hand.

Sheldon: Hello.
Leonard: Hey, buddy, can we have some privacy?
Sheldon: Of course. Wouldn't want to intrude. (takes red bra out of his pocket and hands it to Penny) This is yours.
Penny: Okay, when I'm done with him, I'm gonna need more information.
Sheldon: Nothing odd. I just wanted to rub Amy's nose in it.

Leonard: I'm not being weird. Am I being weird?
Sheldon: Yes. And that's coming from me.