My friends and I are a bunch of pranksters. We do all sorts of crazy stuff to eachother such as break into eachothers' rooms at ungodly hours causing mayhem, newspapering other peoples' rooms, and even kidnapping eachother.
It's all quite simple, basic prankage, really. But I want to do something more clever. I want to sabotage an already carefully planned prank and turn it on them.

There's talk of doing something to this one guy Luke's room while he's away. We can get in, and a couple of the girls have something planned (Plan A). However, knowing about this idea early... I want to turn it around and outsmart everybody else with some kind of counter prank (Plan B). This will mean telling Luke what they're planning first so we can scheme together. However, I want to make sure I have something brilliant in mind first before I scheme with him, to ensure Plan B is a bigger humiliation to its' schemers than their Plan A would be to Luke, if you see what I mean. If I can't think of anything good for Plan B, I'll just let Plan A go ahead and Luke will be none the wiser.

Plan A so far as I know is to just go into Luke's room (let in by his housemate) and give it some crazy makeover, so I was thinking about Plan B involving some kind of booby trap... but I dunno.

Any ideas? This entire post may be quite confusing.... but the long and short of it is... can you think of any effective and humiliating way to booby trap a room?