My dad had a coworker-- 3 or 4 guys all shared the same office but had different departments-- who would walk in every morning an absolute ass to everyone else about being messy, loud, etc. while changing from his driving shoes to his safety boots. It wasn't anything disgusting, just maybe papers on their desks, snowy boots by the door, etc. The guy was just a neat freak and tried to make everyone else in the office the same way. (Yeah, 'cuz that's gonna work. It was damn steel mill.)

So one morning my father stuck a jelly filled doughnut in the toe of the guy's boot before he got into the office. Dude didn't even get a minute to complain, just sat down, grabbed that boot, jammed his foot (ha!) down inside and when jelly shot out of the boot and up his pants leg, he took off the boot and his socks, put his street shoes back on, turned around and went home.

Dude checked his boots before he put them on from then on.