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 White summer dress, and after lifting up the skirt he saw pink granny 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 his Mom's, He decided since he couldn't reverse it he would just have to roll with it. Everyone else saw it as normal anyways.