Sheldon: Were you under the impression that Leonard has no complaints about you?
Penny: Like what? Yeah, yeah, I see you, you're making a little check sign in the air, I got it, just hold your horses. What does Leonard complain about?
Sheldon: Your driving, the plethora of stuffed animals on your bed that stare at him during your amorous activities, your constant tardiness, your singing.
Penny: My singing?
Sheldon: That's actually from my list, but Leonard would be a fool if he didn't agree with it.
Penny: Okay, if Leonard has so many problems with me, why hasn't he just said so?
Sheldon: Because, according to him, you're oversensitive and have a temper.
Penny: Oh, really? Well, then, do me a favor and tell Leonard that he can drop dead!
Sheldon: And she wonders why she's constantly under-tipped.