If your microwaved leftovers are popping and splashing throughout the reheating process, creating the a holy hell of a mess like the one pictured above, it means you have skipped a key step. What you need, of course, is a wet paper towel.
Draping a wet paper towel over the top of the bowl or container housing your leftovers does a couple of things. Most importantly, it contains the food and blocks it from splashing all over the inner walls and ceiling of the microwave. Wetting the paper towel is important because the water weighs it down and helps it stick to your container, creating a bit of a seal and preventing it from blowing off, as a dry paper towel or napkin is apt to do.
As a bonus, it also adds a little moisture into the situation, which can help steam your leftovers and prevent them from drying out as they get zapped.
You don’t need a lot of water on the towel or napkin for this to be effective. Simply run it under the tap for a few seconds, squeeze out the excess, and drape over the top of the food.
This works best with a container or bowl with some depth, so the paper towel is not actually touching the food; draping it directly onto plated food will, in some cases, cause a messy food-sticking-to-paper-towel situation. Though even that might be better than splashing the mess all over the inside of the microwave.