ROFL!
We had a major wish backfire in our campaign, many moons ago...it was funny, but not quite as scatalogically hilarious.
The party had been slogging through a dungeon, really getting pounded, and was on the verge of giving up and retreating, though it wasn't clear that a retreat would be survivable. Falzar, the dwarven fighter, said, "Hey, I've got a ring with a Wish on it. I'll use that!"
So, he wished:
"I wish that all of us were back in my hotel room in City-State...."
That would have been OK, probably...but then Falzar got greedy:
"...along with all the treasure, and all the stuff from this dungeon."
Now, clearly, by "stuff", he meant all the loot, but it was a poor choice of words, to be sure. The DM cackled gleefully...
...and ruled that the party, all the treasure, and every single item and monster in the entire dungeon, had suddenly materialized inside Falzar's hotel room.
The poor walls, floor, and ceiling of the room lasted a moment, then exploded, and the entire inn followed a moment later. An entire tribe of orcs was now loose in City-State, not to mention some trolls, and an enormous purple worm, last seen slithering up a street. The party deemed it to be the better part of valor to scoop up what treasure they could quickly grab, and make themselves scarce, before the authorities traced the sudden monstrous influx to them.