Want to make a wish? Just ask the Monkey's Paw! No strings attached*.
(*) Satisfaction not guaranteed. Wish may backfire unexpectedly.
Just create a post that starts with "I wish ___" and wait for other users to write how your wish didn't turn out how you expected.
If you're feeling inspired, you may even use the wish as a sort of writing prompt.
Example:
Title: I wish for more wishes.
Answer: Granted. A piece of paper the size of a business card appears in your hand with 4 dotted lines for you to fill out your wishes and a little checkbox in front of each.
Now to find someone who will grant those...