The Feminist Stone

The stone he put in its place looked no different, but it was in fact the "Feminist Stone", a cursed item that does grant wishes, but with a pro-feminist (or at least, anti-male) specification. Only if the wisher or the recipient of the wish is female will the bearer of the stone find their wish granted to their full intention. Otherwise, the stone will twist the wording of the wish to deliver unintended and embarrassing results.