Softly, the stranger whispered into Jon's stone, "I wish this stone and only this stone would turn into a hot pink, floor length dress with petticoats, and would only grant wishes to someone wearing the dress."
There was a flash and the stranger was suddenly holding a prom gown on a hangar. He then placed in Jon's closet.
As he was about to leave, the stranger turned back with a second thought. Pulling his own stone from his pocket, the stranger added, "I wish that once those people are no longer wearing the dress, they can no longer make wishes until they put the dress back on." He wanted to make sure that they'd have to be wearing the dress to make wishes.
With that, the stranger left, as silently as he had come.