Jon hadn't just become any girl. He had become a girl identical to Karyn.
As a 9 year old she could have a birthday any time of the year and it would still make sense. But as a 16 year old, the same age as Karyn, she would have to be Karyn's twin--which meant that unless Karyn was aged or deaged or something else weird happened, her birthday must be the same day as Karyn's.
So there was a way to keep the boy from kissing him. Jon said, "Uhh, you're mixing me up with my sister!"
The boy looked over at Karyn and said "Wait, she's Jon? She told us she was Karyn already. We all know you were the only birthday girl who hadn't gotten here yet."
Or maybe there wasn't a way, after all. But it stopped him for a few seconds, anyway. Jon frantically glanced at different spots on the floor until she saw what might have been the stone. She rushed for it, only for the boy to pick it up a moment before she did.
"Oh, your stone," said the boy. It figured--if Jon had a boyfriend, she probably had told him about the stone. And then he said, "I wish we could just have a good time together without the stone getting lost."
He handed Jon the stone, but somehow, Jon now felt different. She didn't really feel the least bit female, but somehow she didn't mind kissing her boyfriend or just having fun at the party. In fact, she found that she enjoyed it....
