Because this stone was actually The Substitution Stone, Zoe's wish was changed to "I wish all the Preps would become Geeks."
Suddenly, to Zoe and Athena's confusion, all of the preppy girls walking around and chattering outside the school became really geeky-looking. Some had glasses, some had braces, all of them definitely looked uglier (not exactly ugly, but uglier than what they looked like before - some had matted hair, pale complexion, acne, etc.), and they all seemed to be talking about science fiction stuff and comic books (something that people like Sarah McMillan really could have cared less about a few minutes earlier).
"Hey, what the fuck?" Zoe uttered. "Those aren't Goths."