"... that Karyn is fully dressed." Blink, and she was. "I wish Karyn was sent back to wherever she was right before I wished her here, and that nobody noticed she disappeared or was worried at all." Blink, and she was gone. Feeling remorseful, he added, "I wish that when she gets home, Karyn will find a bouquet of flowers and, um, a box of her favorite chocolate waiting for her, with a note from me explaining what happened earlier. I wish the note also expresses how sorry I am I hurt her, that I know it was a big mistake, and that I never, ever, would make a wish to make her do something she doesn't want to. Oh, and I wish that no one could understand it except Karyn and me." Blink, and he knew it was done.
Jon had no idea how that wish was granted, but it may have lifted his spirits a little if he knew that the letter was written exactly in his handwriting. No one except for Karyn had ever been able to decipher it. Presumably his teachers just guessed what he meant and moved on.
At some level Jon might have been aware that having sex shouldn't be his number one priority right now, but if he was, he showed no trace of it.
"So, let's think this out," he thought to himself. "I don't want to be a rapist, so I'm not going to wish someone to have sex with me. I don't want to create a girl from nothing, that could have all kinds of implications. I do want to make a girl out of Biff and see how he likes catching, but that's rape too. So, what's left?" Then inspiration struck, or something like it anyway. It wouldn't be hurting anyone except himself, and he could arrange it so he didn't remember anything bad. It'd effectively be masturbation, but with a few wishes, his first time wouldn't have to be as a girl.
After trying a quick experiment to make sure his wishes can be time limited, Jon wished:
"I wish that the following wishes last until the clock strikes midnight tonight:
I wish that Jennifer doesn't think of me as the same person as she is, but instead as a boy she has a crush on.
I wish that I don't think of Jennifer as the same person as I am, but instead a girl I have a crush on.
I wish that Jennifer is horny and wants to have sex with me." Because Jon is totally inexperienced and a bit insecure, he added, "I wish that I have great sexual stamina and staying power. I wish that Jennifer is very sexually responsive, enthusiastic, and easy to please."
He paused, then continued, "I wish that at midnight tonight, Jennifer will be cleaned up and transported back to her bed, with no memory of having sex with me, remembering instead a typical evening alone. I wish that no one at home will notice I have a girl over or interrupt us tonight."
"Whew. That should work." Jon said, not realizing that if he had put that kind of effort in to solving his real problems, he might be much better off. He felt kind of bad wishing all of that on a beautiful girl he has a crush on, but knew intellectually that they were the same person, even if he won't think of her that way for tonight.
As a final thought, he wished away his own memory of wishing for greater sexual prowess and most of the changes to Jennifer. It would all be scripted, but to Jon it would feel (mostly) spontaneous.
(Sorry for the heavy scripting. Much of the detail is necessary for what I have planned for several more eps.)