Swing stone

Little did Jon know the stone his stone was replaced with was the swing stone. The swing stone goes both ways when it grants a wish. It gives the wisher both their wish and an aspect of the opposite. If Jon was to wish to be a woman he'd mostly be a woman, except for one male trait that would be enhanced. So he could end up a shemale, a hairy woman, a muscle girl, a girl with a very manly male personality, etc. If Jon wished to be bigger he would be bigger, except for one thing that will shrink.