I don't have any plans for it these years, but I used to have a lot of fun with it when I was younger.
My favorite prank was twisting the showerhead the night before so that it was angled towards the open shower doors. In the mornings, my father would pull the shower pin immediately after turning the water on, rather than letting the water run for a while to allow it to heat up.
It would be 7:00AM and I'd hear him turn the water on, pull the shower pin, then engage in a mad scramble to turn the water off while trying to avoid being blasted by ice cold water first thing in the morning