At my boy's swim center, there is an area where they set aside old, defunct, unneccessary, etc, diving boards. One has been there forever and is secured to the ground (no idea why) and doesn't bounce (probably the wrong term--it doesn't go up and down). My genius daredevils decided during freetime from a meet to try to do one of their sister's beam routines. It was hillarious, especially because all the other little boys were crowding around, trying to do it themselves! We had to break it up quickly though...concrete, young bodies, and gymnastics is probably not the smartest combo.
They also like to do handstands on the diving board, which they always get yelled at for.
My girls are notorious for one day in kindergarten when they decided not to walk in line, but to try to do cartwheels in line. Silent lunch for both of them for that one.
'Course, it is all so cute that you feel bad punishing them.