Probably the most fun one can have at a Hotel is to get up before the cleaning staff arrives, and swap all the "Do not Disturb" signs about. Move them between rooms, remove them, or if you hear "action" in the adjoining room, flip the sign over to "please make up room". Nothing better than having the maid walk in on that noisy couple who have been keeping you up all night.
Of course once the cleaning staff walks in on a few couples, including the mandatory pair of dudes, they become wholly paranoid, and you cannot get decent service on your floor. But that’s the price we pay for good sport!