One of the three guys I live with never really leaves his room or goes away. So for the first time since we can remember he went away for the weekend meaning it was time to strike.
Classic cling-film-room prank, used about 9 rolls of cling film, almost two hours work. Did absolutely everything in his room; mattress, pillows, duvet, clothes, all 200-odd DVDs, rubbish on the floor, everything. Cling filmed his door shut from the inside and climbed out the window.
One of my other housemates rigged up a webcam and recorded it. I think you can see for yourselves he didn't appreciate the efforts we'd gone to.
http://www.youtube.com/watch?v=tKkbI75k6sI
He's never had a sense of humour but we didn't know he'd be this bad - he didn't come out of his room or speak to us / see any of us for a week!
Annoying he found the camera quite quickly, but there's a few seconds of gold in there.