There was a flash of light and Jon could feel his clothing changing. After the light faded and Jon could see again he saw himself in the mirror wearing a brown pleated mini-skirt and a pink tank top, he could see black bra straps through his shirt and after lifting up his skirt he saw white panties.
Jon realized that he hadn't thought his whole wish through, this would be sexually exciting, but it would still be very weird. He would be wearing girl's clothes Sarah's, who everyone knew dressed very provocatively. He decided since he couldn't reverse it he would just have to roll with it. Everyone else saw it as normal anyways.