Ahh, nothing wreaks of good old juvenile tomfoolery
than simple, cheap pranks on those with whom you live with. Remember that picture where some wise-guy drew on your face with Sharpie while you were passed out? This Instructable gets you one step closer to redemption and all it will cost you is about 7 cents +/- (which you may get back).
Let me start by setting the scene: your jerk roommate is in his/her room asleep or otherwise not paying attention; their door is closed. You are about to exact revenge with ninja stealth.