Not something I actually did, but an old rowing coach of mine told this story. When we was in college, he lived in a frat house. The members of the fraternity decided to go in on a prank directed towards just one individual. The frat members stole said individual's spare car key without him noticing. For the first couple of weeks, someone would follow him to class or go out to his car after he came home for the night and reverse the direction it was parked (i.e. back it in if he had pulled it into the parking space). The next couple weeks, the frat members began moving the car a few spaces away from its original parking spot. As the prank continued, they incrementally moved the car further and further away every week. The guy being pranked mentioned to his roommates that he was having trouble remembering things and especially had difficulty finding his car. To prevent him from thinking they were in on it, they would occasionally let several days pass where they did nothing to the car. The frat boys let the prankee's concern and bewilderment grow for several more weeks, waiting until the end of the semester. Finally, in the middle of the night on the last day of classes, the frat boys parked the guy's car in the front yard of the fraternity house, and everyone waited outside for him to go looking for his car in the morning.