Jon considered both his sister Zoe and Sarah McMillan. Zoe, was dark and and quiet, while Sarah had always been loud and upbeat. Jon knew that being a goth or preppy didn't affect how nice a person was, Jon had always been fascinated by how different girls with those personality types could be.
Jon considered making a wish based on those differences. He wanted to make it reversible so that he could undo any lasting damage that might occur through a poorly phrased wish.
"I wish that, for at least one week, and that I can reverse this after the week if I so choose, that there would be two basic types of personalities: goth girl types and preppy cheerleader girl types. While there would be 'ranges' of behavior for each of these personalities, everybody would be very obviously goth or preppy type. There would be a strong competitive streak between Goth's and preps, but there would be certain common themes that would cross boundaries: both would be sex-crazed, have a passion for sexy underwear and would unconsciously act as sexy and flirty as their personality would allow. They would also find each other attractive; Goth's would be attracted to preps and vice-versa.
The stone flashed, telling Jon that his wish had been granted. He assumed that Zoe would still be a Goth and Sarah would still be a prep, but wondered how other girls, like his tomboy friend, Karym, or his mother, would change.