One amateur mechanic wired up the brake lights in his dad's car so that when the brakes came on, the horn sounded.  That'll teach Dad not to loan junior the car.  The next time Dad pulls up at a stop sign, he blasts the car ahead!  The car ahead naturally assumes Dad is being impatient, and turns around to glare at him.  Dad assumes the car ahead is parking instead of going, and really does blow the horn.  Well, you can see where this starts to lead.