Jon thought over the many things he could do with the stone. What would it be like if he could swap people's personalities, for instance?
But then he got an even better idea. If he was curious as to what it would be like if one person had another's personality, he didn't have to swap. It wasn't as if a personality was some thing that there had to be exactly one of. Couldn't he just wish that several people had the same personality?
He just had to decide who.