"Ok, ha ha, Karyn. Seriously, you saw me change, right?"
Karyn stopped laughing and looked at him seriously. "No, you didn't change. You're pullin my chain, right? Either that or the gun just makes you think you changed. You can see that you're still a girl, can't you?"
Jon put the gun down and picked up the stone. "Yeah, uh, heh heh," he laughed nervously. "I wish I knew what happened." After a moment the lightbulb went off over his head.
He heard the voice of his grandfather in his head as he remembered reading the note left for Jon; "...but beware for the words of a wish can be reinterpreted but not changed once the breath is over."
And then he heard his own voice making the wish about the reality setting; "I wish there's a setting so I can change clothes or not, and a setting to change reality or not--if I change reality only me and Karyn remember what happened." And he distinctly heard himself take a breath right before adding that last part about only him and Karyn remembering what happened.
Finally, he realized that the gun would work similar to the stone, but only the person actually firing the gun would know that anything changed unless it wasn't set to change reality.
"So?" Karyn asked expectantly.
"Um, it didn't work quite the way I thought it would." Jon was still a bit weirded out by his voice. "But that's ok, lets try it out on Zoe afterall."
Karyn accepted it and smiled. When Jon added, "Lets go get her now," she turned around to walk out of the bedroom.
Jon quickly picked up the gun and fired it at her and watched the green glow engulf her and change her in a fraction of a second. Then to stop her he said, "Oh, uh real quick, does this skirt look ok with this top?"
Karyn turned around and Jon could see she was definitely a guy, except she still had large breasts and long blonde hair. Karyn looked critically at Jon for a moment and then said, in a weirdly masculine voice, "Of course. Everything looks good on you. C'mon, lets go get Zoe."
"I'll have to figure out why she still had tits later," he muttered to himself, and another zap as Karyn turned to leave the bedroom and she was back to her female self. Jon changed the setting on the gun to not change clothing and then picked up the stone and caught up with Karyn out in the hallway.