It’s easy; people have played it here before. Take the wish of the poster above you and corrupt it.
I wish I could turn invisible on command.
You’re waiting at the DMV
I command you to be invisible.
I want a custom fitted suit.
I’ll just peel off your skin and use it as a template…perfecto!
I wish I was a little bit taller.
You now have a small drill bit protruding from the top of your skull.
I wish I could dance.
You never mentioned anything about stopping.
I wish I more cheery.
You now don the uniform of a high school cheerleader-and are transported to the glee section of your most hated rival.
I wish for a tuna-fish salad sandwich.
Ewww, I think this tuna sandwich has gone bad… here, taste it.
I wish the Cubs would win the World Series.
Okay, but first they’re all going to head North and call themselves Brewers. 
I wish I could fly.
You can fly, and it is glorious. But your hips and ankles are not well-made for landing, and each time you do they wear out a little. You will not know this until you are 55 years old and facing a long painful retirement.
I wish I could run away and live a life of wealth and refinement.
The fate reserved for the most pitiable slaves is working in the gold smelting facility.
I wish I didn’t have to go to work today.
I give you wealth but after only one day you find out wealth isn’t this, it’s this. The resulting injuries, as you are not a cartoon, prove fatal.
I wish I was a cartoon.
A. You forgot to make a wish.
B. Goddamnit you people are clever.
You don’t. You’re in prison.
LR, need your wish man.
Nobody corrupted Joey P’s desire to be a cartoon. Do that one instead and then make your own wish.
You’re trapped in a piece of digital media and can only perform the same scripted actions forever.
I wish I had new carpeting.
POOF! Too bad the contractors don’t speak much English, and tacked that snazzy new Brady-Bunch era olive green geometric pattern (“hides stains!”) onto your walls. Enjoy!
I wish my fat cats would let me trim their claws.
Your cats let you trim their claws, because they have become so fat that they can no longer move.
I wish I knew what I wanted to do with my life.
You know exactly what you want to do, and that’s have sex with small children.
Speaking of, I wish Starving Artist would go away.
He does-to all of your other favorite internet boards and hangouts.
I wish I had a perpetual motion machine which would give me free energy for life (and thus take me off the grid).