Here's how it works:
You quote the previous poster's wish and then grant it. But in granting it, you cause the outcome to be unpleasant, undesirable, disastrous and tantalizingly in direct opposition to what the poster wanted to achieve.
Then you post your own wish for the next person to grant.
Here's an example:
Wish: I wish I had all the money I could ever want.
Quote:
Wish: I wish I had all the money I could ever want.
Granted. You have all the money you could ever want. In fact you acquire more money in a single day than you could ever hope to spend in a life time. Unfortunately, all that money has come from everyone else in the world, which causes the world economy to spiral into abject poverty. Factories close, farms turn to wastelands, and you quickly discover that there's nothing to buy. Humankind eventually dies out, and the predominant life forms become insects, mice and mold.
Wish: I wish I could eat lots of ice cream and not get sick from it or gain weight.
