get an carrier bag with no holes in it fill it with water and put their boots/shoes/trainers in itand place in freezer. Obviously tie the bag first. We used a bin bag I think.</p>
Not sure if it will work with a seramic toilet, but put a 9volt battery in the lavvy, then when someone pisses in it, it sends a shock up their cocks! Like i said, ive only tried it in one of the metal urinals in my locals toilets...and it was piss funny!!! Putting Immac(or whatever its called now) in the shampoo bottle might raise a chuckle...
Put powdered Milk/Baby Milk on your mates bedsheets...he'll sweat in the night and stink of sour milk for ages after,,,,