Myself, I'm prankishly impaired, but I was told this one many years ago and always thought it had a certain touch of finesse.

One day, when a street construction crew had gone off to the tavern for lunch, a group of bright college guys with the appropriate hard hats, signage, etc. proceeded to detour traffic for several blocks and ultimately to guide the cars down a dead-end alley, where they were stuck, causing a large grid lock and lots of consternation for the city fathers. The college boys were suspected by the police, but there was no proof.

Several weeks later a bona fide construction crew was working in front of the college. Seeing their opportunity, the college guys called in anonymously to the police station and reported that a bunch of college guys were dressed up as workmen and pretending to do road work out in front of the school. Then they ambled out on the lawn and watched the ensuing fracas when the police arrived and tried to arrest the real workers !