"What the fuck, Sarah?" shouted Jon in a Sarah-like voice, "What possible reason would you have for wishing that? I'm still bigger than you!"
"I don't care how big you are," squeaked the little woman, "You're small enough and your boobs are big enough that you're going to want to find a way to reverse that wish as much as I do."
Jon was actually a little impressed by Sarah's thinking here -- not that he'd ever admit it. Instead, he looked around at the double-sized world of Sarah's room and down at his double-D sized chest. His mind raced for a solution.