I usually try to keep my microwave clean. We don't use it a whole lot, so I try to make sure that if I notice it is dirty I clean it. I also always keep a paper towel on the turn table, which help keep that part clean and easy to wipe up if something spills.
On Saturday, I was fixing a quick lunch for the kids and I handed Jeff a hard boiled egg for him to use as part of his lunch. He wanted it warmed up, so he put it in the microwave and fooled around with it setting the time to 10 minutes (he knew it wouldn't take that long). After several seconds the egg exploded with a loud pop all over the microwave. I hadn't thought to tell him that eggs are real sensitive in the microwave or that he probably should have cut it first. Needless to say, we had a good laugh and he had to clean the microwave.
The moral of the story is give someone something that will explode in the microwave and then they get to clean up the mess along with anything else that was needing to be cleaned up in there.