"I wish Karyn was here," Jon said. He wanted to make sure she was around when he made his wishes, otherwise her memories would change to fit the new reality.
The stone glowed, granting his wish, but instead of Karyn just appearing in his bedroom (like he expected) the stone began to change right before his eyes. It grew larger and larger until it was almost as tall as Jon, then it took on more of a humanoid shape, then the shape became obviously female. The stone's color and texture changed until it looked like human skin. And then Jon realized what the final appearance would be. It was Karyn. The stone had become Karyn.
"Karyn?" Jon asked, after the stone was done changing. This Karyn looked like the original one, the one before all the wishes, the one that was a redhead and had B-cup breasts. It was the Karyn that he pictured in his mind when he made his wish.
"Yeah?" she asked back. "Jon, what's wrong? Why are you looking at me like that?"
"Karyn. You're ... the stone," Jon uttered. He wondered how she'd respond to that.