Mom Had Quite a Mouth on Her

Customer: How you doin'?
Postal worker: I'm working harder than a one-legged man in an ass-kicking contest.
Customer: Sounds pretty bad.
Postal worker: Well, it's better than my mother. She used to say she was working harder than a one-legged whore working both sides of the street.

--Grand Central Post Office, 45th & Lex