The dog days of summer often encourage mechanics to find ways to entertain themselves during breaks and lunch hours. Some of the pranks they pull on each other can be creative.
I remember one young feller who spent the better part of a week rebuilding the final drive in a four-wheel-drive tractor for the first time. He was nervous as a cat as he drove it out of the shop. As soon as he pulled it around the corner, one of his buddies took the 5-gallon bucket of used gear oil that had been drained from the final drive, and carefully dribbled a stream of that oil from where the tractor had been parked, all the way out the door and across the lot. When the victim walked back in the shop and saw that string of oil on the floor, it was like one of the old cartoons where Tweedy Bird does something to scare or shock Sylvester the Cat--y'know, where Sylvester's eyes jumped out of his head and bounced on the floor?
The prank that is legendary at our dealership happened when I first started working there. I finished working on a combine and was nervous about my repairs. I had it sitting outside the shop, running at full speed, while I walked around and inspected my work. Unbeknownst to me, another mechanic snuck into the cab and started to pull the diesel fuel stop. Not enough to kill the engine, but just enough so the engine started surging and stuttering like it was trying to puke a piston. I skinned my shins and about killed myself trying to scramble up the ladder to shut off the engine before it self-destructed, only to find that co-worker laughing hysterically.
Yessir, that was a classic prank. Good thing I'm not a vengeful person, the type who would wait YEARS for the perfect opportunity to repay a debt...tick, tick, tick.