"I wish that Sarah was here with me."
Suddenly a very surprised Sarah materialized in the center of the room. She got her bearings as Jon made his wish, and tried to grab the stone, but she was too late.
"I wish." said Jon, "that Sarah has a cock and wants to fuck me and can't get rid of it or stop wanting to fuck me except by fixing all the wishes she made on me." Then he tossed the rock onto his dresser.
There, that should do it, thought Jon. He got what he was now craving, and had a chance for Sarah to stop it. Sarah looked horrified, but found herself drawn to Jon. She looked between the rock and Jon, not sure whether to use the rock or have sex with Jon, and finally faced Jon, stripped herself naked, revealing a cock between her legs....