As Jon slept, the magic of the stone began to take effect. The stone began to glow, and a small light came out and floated into Jon's head.
Now, a wish for something interesting could be taken in many, many different ways. Different people found different things to be interesting, so it could take many different form. But above all, since Jon was the one who had made the wish, the effects of the vague wish would have to adhere to Jon's own deffinition of interesting.
So using Jon's thoughts, the wish would use things he found interesting as a basis. But most specifically, his forms of entertainment. What he watched, the kinds of books he read, what games he liked to play, the stone's magic searched for appropriate elements. Once it had what it needed, the light left Jon's head, and began to shine brighter, and expand, and engulfed the town, altering reality to be more like the elements it had taken from Jon's interests, and as per the rule, only Jon would be aware of any differences.
