The wishing stone glowed. And when the light dissipated, Jon saw that everything shifted. All of a sudden the wall was higher and he felt off balance.
Looking around showed him that it had worked something like what he had expected. The mirror and a quick look down at his own body showed that he had transformed into Sally. There were a lot of ways to interpret "switch lives with", but certainly being in Sally's body was one of those ways.
And he supposed Sally was in his own body. But she didn't hear the wish. At least not all of the wish. People who didn't hear the wish thought the result was reality--she'd think she actually was supposed to be in Jon's body. She'd think she was Jon!
And what were the conditions that would end the wish anyway?
Jon left the bathroom to see his own body standing there. Sally? It had to be, but with wishes she wouldn't remember being Sally. "It's all yours," he said in Sally's young girl voice, as he exited.
"Jon" frowned as "Sally" passed by. He looked the same, she looked the same...what had just happened?