Two teachers at my high school started a practical joke war that culminated in a junk mail war of huge proportions. They finally called a truce and got it cleared up and the mail stopped, except for the military mail that one had signed the other one up for. He wrote (honestly) that he had graduated from a fine college and was interested in the Marines, Air Force, etc. etc.
When I left, about two years after this, he was still getting phone calls from 2-4 times a month.... they were very persistant even over the (loud) objections that he was 45 and not interested in a career change...