Electric Urinal

Much like when Rabb pee'd on the Electric Fence you Rigg a Urinal, or a Toilet to have a slight Electric charge. Not enough to cause damage but enough that they'll feel it and get a good shock.

Someone goes to the bathroom in middle of the night, or whenever they're jolted.

You can always add to the prank by having someone push them into their pee or the toilet re-shocking them idk.