Once his wish was completed he perceived a flash. It wasn't truly a visible flash, or even truly something he felt, or heard, but more like a soft encompassing of his entire being by a background of various forms of white noise.
When it was over.... well, he felt different.
'Did it work?' Jon tried to move... but he couldn't. He tried to look around, but all he saw was a vaguely-lit blackened haze.
But he could hear. He apparently couldn't hear very well, since the sounds of things like car horns and deep, rumbling music seemed muffled at best, but he could hear.
It was the voice of some guy. Jon recognized the voice, but didn't place it right away. But he could, though just barely, make out what he was saying.
"So Zoe, you ready for tonight?"
The girl's voice that came after that was even more distorted than the first, Jon supposed that it was because he was literally attached to the body of the person making the sounds, and liquids and solids carry sound differently from air, thus distorting them, though he could still tell what was being said, "Yeah, of course."
"Great." There was the sound of a car door opening, and the sounds of music intensified as Jon was pulled around.
"Thanks." Jon's face was then planted into the fabric that was preventing him from seeing anything, a piece of fabric that Jon assumed to be a pair of panties.
It would seem that Jon's wish had chosen the nearest vagina for Jon to become, and despite that she was outside the house, that just so happened to be his little sister Zoe, who was even now headed out for... well, he really didn't know what.
Jon had never wanted to SEE his little sister naked, but being his sister? Let alone having his entire consciousness confined to that very specific part of her body... he wasn't really looking forward to it.
'Man, now I wish I hadn't made that wish... and I've got a whole month to go!'