Okay so I've seen this on other forums. Okay so here's what you do.
Poster 1 posts something they wish for.
Poster 2 grants the wish but makes a condition that corrupts the wish.
Poster 1: I wish I had a new car.
Poster 2: Granted but the car explodes when you look at it
I wish for a cat!
[Sorry if this has already been posted here I didn't see a topic for it.]