Penny the doors shut (if the doors open inward) you shove pennies in the door jam so you can't get the door open
Freeze ballons in liquid nitrogen (ballons that are inflated) and shove them under the door, then when the person opens the door, they have a ton of ballons in their room although the door was locked.
Take all the supports out of the bed that way as soon as they sit on it, it falls in.
Get a Universal Remote and go to the window of someone watching TV and change channels.
The next time you have a party be sure to stock up on super glue. When the victim falls asleep put the
super glue on their zipper of their pants
ALL TIED UP- Make sure that the doors in the dorm open inward. Take some heavy rope,
and tie sections of it too every door. If done properly, no one will be able to leave
their rooms.
Get one of those boullion cubes, made for making soup, and put it in your buddy's showerhead. A broth bath first thing in the morning can be a real drag.
Take a large bottle of industial strength washing up liquid, this can be bought from any supermarket, and pour it in the top of the toilet (where the water is kept). When the victim flushes the toilet, the bowl and eventually the room will fill with lovely bubbles.
The list goes on and on