The idea is basically that poster A asks the evil genie to grant a wish.
Poster B grants the wish, then makes one of his/her own.
Of course there is a catch
The genie always grants the wish, but with an evil twist
Example
Post A - I wish it would rain today
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Post B - Granted, but it rains so much, your house is washed away, and you end up living under a bridge.
I wish I had a million dollars
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Post C - Granted, but the money comes out of a mobsters bank account, and he sends several large men to visit you
I wish.....etc
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So first wish....
I wish I could fly...