"Mike," said Jon, "what do you mean use the stone?"
"Your magic stone! I saw you had one. You were with Karyn trying to use magic on tree branches. I was with Sarah with a lot of other guys from the football team, but I happened to be listening to you and I noticed the wish about Karyn's hair and breasts. It's the only way I can change back."
"But what happened to you, Mike?"
"I don't know. Some kind of weird magic. As soon as it happened to me I realized you were the only one who could change me back, since I knew you had something magic too."
Of course, thought Jon. It was simple.
Jon's first question was about how Mike knew he was changed. It was simple. While wishes change reality, sometimes the change is just "this weird magic thing happened". It was like wishing to have a million dollars--the wish wouldn't make people think he always had a million dollars, the wish would just make it appear by magic.
Jon's second question was about how Mike knew about the stone. This was even simpler. Sarah and some football players were there when he and Karyn were making wishes. Mike was a football player. He saw Jon.
"I admit it," said Jon. "I do have a wishing stone, but I don't know if I can change you back."
"Please, man, do something!"
"Fine," said Jon. "I wish that as long as Mike is like this, he's perfectly happy being like this."