This is a fun one: Someone makes a wish, and the person below corrupts it (The more clever, ironic, and original the better.). That person then makes a new wish in the same post and the person below follows the tradition.
(OOC: Yeah, does this mean I make a wish that sounds like yours, just Dookie-fied?)
No, see. I'll show you.
Me: I wish for an alien invasion.
I: Granted, but the aliens are invisible and are identicle to frogs. So, there's virtually nothing interisting that arises from the alien invasion. I wish for the ability to become invisible, and to become visible again.
Someone: Granted, but when you're invisble you're dick isn't and vice-versa.