Not an April 1st prank, but years ago I lived a few doors down (in a college dorm) to a guy who was always bragging about his "success" with the ladies. One afternoon I had a female friend of mine call him and represent herself as a nurse at the school's student health service clinic. She told him he had been identified as an intimate partner by a girl who had tested positive for a social disease. She further told him he needed to report to the clinic to be tested, and if necessary, treated. He was also told he would need to provide a list of any sexual partners he'd had since the school term started. After hanging up, she described him as in a state of near panic.
Within minutes we heard his door open/close and then watched him out my window head toward the clinic. What happened when he got there we never found our since he never mentioned the call and subsequent clinic visit to any of us on the floor. He was noticeably quieter thereafter about his conquests, however.
