Jon made the split-second decision to tell Max the truth.
"We've met before," she started. "I'm Karyn's friend Jon Gibson. Yeah, I looked different the last time you saw me..."
And she went on, explaining about the rock -- leaving out Karyn's accidental wish -- and how Sarah McMillan had stolen it, and the wish she had made that Jon would acquire some qualities of any girl he sees that he finds attractive.
"Then she wished me to a strip club where I was getting a lap dance. All I could think to do was run over here where Karyn might be able to help me. I accidentally looked at a couple of women on the way over here, including a 'Tomb Raider' poster..."
"So you're part stripper and part Angelina Jolie," finished Max, looking impressed. Then he realized, "But if the stone works like you said, why don't I remember you always being a girl, looking like that?"
"Sarah didn't specifically wish that I'd turn into a girl," said Jon. "She just wished I'd gain the qualities I liked from attractive women I saw. Seeing the naked stripper is what turned me into a girl."
"Ah. Hmm," said Max. He put his chin in his hand for a moment, then brightened. "I've got an idea."