What is a comeback to what's up?

Answer 1

just say "SHUT UP that's what i said to your mom last night."

OR

just shrug your shoulders and walk away

say, "I don't shut up, I grow up. And when I look at you I throw up. Then your mama comes and licks it up.

Answer 2

"gas prices" or "the sky" work well but people are generally confuzed with the first