John had a small problem. He had a thing for Karyn, but shortly before the ceremonies had begun, a thought had crossed his mind. A thought that had been inspired by a pornographic movie that he had seen once.
Then John realized that he could make that dream come true using the stone. He could be with Karyn in one of his fantasies, but he needed a cover so that she would not suspect that he had wished for her to turn into a donkey woman. So John had conjured up this wizard using the stone and had wished for him to start mutating the women at the ceremony into donkeys.
This is where John's big problem started - he hadn't been specific in his wish when he had created the wizard, and the wizard was now thinking for his self, and thus straying from John's original plan...