The stone he put in its place looked exactly like Jon's stone, except that it wasn't. It was the Nerd Stone.
With this stone, the user's wish would be twisted, ranging from slightly to majorly depending on the wish, into a geeky version of the wished for result. Furthermore, who ever had made the wish would become just a little stereotypically nerdier/geekier than how they were then with each wish, until they eventually became the picture poster-child for the timid, shy, clumsy, short, scrawny, nerdy/geeky stereotype.
Also, every time the same person made 3 wishes in a row, everyone in reality, no matter their status, would become 10% nerdier/geekier.
And as a final bonus, the nerdier someone got, not matter how they were affected, they would find themselves more and more romantically/physically attracted to nerdy individuals.
