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 he (loud) objections that he was 45 and not
interested in a career change...