My brother-in-law, a pilot, related this incident between a fellow pilot and an engineer/mechanic at the airport. These two chaps were forever squabbling and trying to drive the other one nuts. The pilot once turned a plane in to the shop with a complaint that read "Unfamiliar noise from engine." The next day, the plane was ready for him. The engineer's logbook entry read "Ran engine continuously for four hours. Noise now familiar."
(From the "Rest" of RHF)