When my uncle was in college, he pulled loads of pranks. One time, he put live frogs in his friend's dorm room while he was away. (It wasn't until the guy got back that they discovered that he is afraid of frogs)
Another time, he and some friends crumpled loads of newspaper into balls and tossed them into a dorm room while the inhabitant was away (It may have been the same guy, idk). By the time they were done, there was paper from floor to ceiling.
But my personal fave of his is when he completely covered another guy's dorm front door with newspaper one sheet thick. When the guy opened the door, there was newspaper covering the opening. (The door opened inwards.) They did this for several days, always when the guy was asleep. Finally, he stopped tearing through the newspaper and just walked straight through it. The next night, they leaned a couch on its side right outside the newspaper. When he tried to walk through it, he ran straight into the couch!