Now microwaves have been around for a while now, yes? Then why do people still not know how to maintain them so that they don't gross out their coworkers? The microwave at work looked like someone had thrown up all kinds of nasty shit in it. Obviously covering the food while heating it is not a concept that most have caught on to, or cleaning up after yourself for that matter.
The place doesn't need a sign that says "Please clean up after yourself cuz your mama don't work heya" (imagine that one in a southern accent). It needs:
"My cat is more respectful than you because she eats her own vomit."