Jon couldn't believe it. His sister Michelle is really a guy who was transformed with the stone?
But at leats he was glad he had the stone back. He had barely even noticed it was missing.
And he, at least, knew how to reverse Michelle's wish. He could just say something like "I wish that Gina wouldn't see Mikey get a 'woody' because she would always be looking somewhere else, not because Mikey is a girl."
He could--but he wouldn't. At least not yet. That stone was very powerful, and stealing it could cause a major disaster--even worse than his brother/sister changing sex. It was just luck that Michelle had come back to Jon with it at all.
So how could he prevent Michelle from causing trouble, or at least teach her a lesson?
"I wish," said Jon, "that first of all, Michelle remembers that this wish has changed her, and second, that..."