Once I put a ball of chassis wax (the coating that truck chassis come with...this really waxy black stuff) onto the earpiece of a co-workers phone. It took him forever to find out why his ear was always smudged black every day.
Seriously, something I do at work. I leave these ridiculous signs every now and then. Typically in the bathroom.
There's one there now on an empty clipboard that is hanging in the bathroom that has been empty for a year (used to be for a janitorial checklist). The sign states "This is a load bearing clipboard, please do not remove." When someone does remove it, there's another sign underneath...
They built a "smokers shack" that is basically a "bus stop" shelter. I put a completely fabricated bus schedule in it one time (that didn't last long).
I put a sign that said "For Reference Only" next to the thermostat for the HVAC controls in the office (stupid quality system humor FTW!).
I post EVERY certificate I've ever received on the wall of the cubicle. [looking over shoulder] I've got certificates for:
"Stay Current on Electrical Hazzards"
"How to Avoid Electrical Accidents"
"What is Lockout/Tagout"
"Preparing for and Performing a LO/TO Shutdown"
"Southwest (airlines) Boarding School"
"Distinguished Service Award (3 years)"
"Bomb Threat Training Checklist"
and a few others...
Clem