When I was in grade school someone called in to all the local radio stations and social-engineered a snow day for our school. They made the announcement on the air that the school's boiler had broken down. We all heard it over the breakfast table, and my brother and I got all excited about a day spent watching cartoons and playing outside in the snow.
Then about an hour later, the radio station announced an update which said that listing our school on the cancellation roll had been a mistake. Our school really was open that day, so my mom made us hurry up and get ready, then she drove us to school. We were pissed.
When we got there, only about 25% of the students had even shown up. Our first period classes were pre-empted for an asinine discussion led by our teachers, a flimsy investigation of who'd called in the day off and telling all of us to snitch if we knew anything. The principal even made the rounds to all the classes, raking us over the coals and then giving a lecture about how bad it was to play such pranks. After that, we had pretty much a blow-off day. Few of our classes were even conducted normally. Mostly we just sat and had class discussions about various topics.
As far as I remember, they never even discovered who it was that called in the snow day. I don't know if it was a student or a teacher or what, but it was apparently somebody close to the principal's office, because they knew exactly what to say to all the radio stations to get it announced. Whomever it was, he/she was a major hero in the eyes of most of the students.