Its easy to do.just go to the dark garden and dig up a skull with knuckles or rouge(pumpkins and egg shells work too)place the skull,shell,etc. on top of 1 of the four tombstones that you can stand on,and it will fall off,bounce,and repeat.it will not work if you run into it to stop the bouncing.

glitch-stuck.in the hero garden,there is a piller(spelling??)and some chao start there when you enter the garden.put a chao there and it will be stuck.(it will make a really annoying noise though...)