Knowledge enlightens

On the way home Karyn clenched the rock and said "I wish Jon remembered every wish I had made at the dance" Suddenly Jon remembered that he was suppose to be a guy "Karyn what the hell was that give me the stone I need to fix it" Karyn sheepishly handed the stone over "Good now I wish I would switch lower halves with Sara McMillan" Nothing "I wish I would revert to how I was before the dance" Nothing "I wish I knew why my wishes where not working " Suddenly in Jon's head she heard the answer they could not switch back because Sara was hit by a car when she ran crying out and a long time ago a wish had been made that a person could not use the stone to toy with life and death until they where mature enough to handle it.