Back when I was a first year apprentice and was working at the retirement home, decided to play a little prank on our foreman.
Another apprentice and I were busy vacuuming out dirt and sucking in twine into all the underground feeder conduits when we got the bright idea to get the plumbers in on the prank too and pull a twine through one of the floor drains and tie it off elsewhere..
Immediately summoned our foreman and showed and told him that:
"When we vacuumed string into the pipe going to the west wing, the floor drain in the west wing shower room started to whistle so we put the string in anyway, and also Peter the plumber is having trouble with one of the toilets in the same area, said something about augering up some kind of wire out of the drain or something and would like to talk to you about it."

I swear, I have never ever seen someone get that worried / panic look on their face quite like that ever in my life, it was PRICELESS! Wish I had a camera THAT day!

A.D