"I wish I were a girl." The stone didn't discuss the fine points of the subjunctive usage and explain to Jon why that was still proper English. It did, however, transform Jon. He wasn't instantly clad in a dress, but he did suddenly have longer hair, lipstick, earrings, and every inch of himself felt slightly different. Or more than slightly, in some places.
"Jon, take off your clothes and let's do it. I want to, whether you're female or not..." Puzzled, he added "How did you turn female, anyway?"