what to say in response to “what’s up”

hmmm….

I think the sky’s up

Oh, the Disney/Pixar’s ‘UP’… Well, there’s this boy, and an old grandpa…… (continue with it until they get annoyed)

[Do a headstand or or bend over and stick your head between your legs and say]: I don’t know… which way’s up?

philosophically, i do not believe in ups or downs, nor wrongs or rights so to me this question in meaningless

up is the direction in which things are above us.