It's Right Up There with "Who Shot JFK?"

Metro-north conductor: This train has five cars open.
Drunk teenage girl: Your mom has five cars open! Your mom's fellatio lips are open too!
(trio sits in row in front of girl and friend)
Drunk girl: I hate you, don't sit here. We're all going to throw up on you. Why are you still here? No one likes you.
Girl's friend: Why are you so drunk?
Drunk girl: That's something we'll never know.

--Metro-North