"Wait a minute" said Jon, "why is Tiff-Bev human now?"
"Oh" replied Karyn. "That wasn't from Sarah's gun, so I had to wish her back. You didn't hear it? I just wished she would be human and that the first wish would come true by her being bitchy to Sarah, which she was, anyway." (Yeah, fixing my mistake -Hikaru)
Christy made her own wish--no stone necessary. "I wish that Sarah would have the lower body of a pig." Nothing happened, but Karyn had arranged it so that everyone knew the limits of the wish, and Christy was quick to change the wish. "I wish that every day, Sarah would be a random farm animal from the waist down." Which included both chickens and pigs.
As the next person in line forced Sarah to lay eggs, Jon and Karyn both decided they no longer wanted to watch, even if Sarah had done worse to the class before.
"I can't think of how to fix the teachers" said Karyn. "Here, you try this."
"I don't need it" said Jon. "You saw how Tom gave the class wishing powers. I wish that though the teachers are teenagers, that means they have more years of life ahead of them like teenagers but their bodies look the same as before."
"Hmm, that's right" said Karyn. "We both have wishing powers. What do we do with this stone? It's useless now."
"Maybe Zoe would want a wishing stone..." said Jon.
"Naaah. If you want to give her the power of wishes, just give her wishing powers, same as Tom."
As Jon walked home, he realized someone was behind him. He turned to see his sister Zoe, walking home from school. But there was something strange about her. She had unusually large breasts, her goth makeup was gone, and she was wearing a low-cut green dress that very much didn't match her personality.
"Zoe?" he asked. "Is that you?"
Tears started to appear in her eyes as she walked on past Jon without saying a word."
"I wish I knew what was going on here" said Jon. Zoe had been transformed by a wish from Tiffany-Beverly, who was pretty snobbish and didn't much like Goths. She had wished that Zoe would look and act like a proper woman from before the 50's.
Jon was already starting to get good at reversing wishes and the fix didn't take too long. "I wish" said Jon, "that the wish used on Zoe would refer to the 2050's, not the 1950's, so Zoe's just like she was before." When Zoe changed back, he told her "Zoe, I think there's a problem here... I wish the other students' wishes couldn't be used on you against your will."
The sensation of a completed wish was missing. Jon realized that modifying how other people could use their wishes must count as affecting the other people, which Tom had prevented. Jon tried it with the rock instead of with the Tom-granted wishes--and this time it worked.
"What was all that about?" asked Zoe. "She just commanded me and I had to do what she said!"
"I told you there's a problem" said Jon sadly. "Everyone who was in Sarah's class now has the ability to make wishes. And Tiffany-Beverly is abusing them. Too bad Karyn changed her back--we could very well have a new Sarah here. I wish I knew how Tiffany-Beverly was using wishes today."
Jon grimaced.
"Jon" asked Zoe, "what is it?
"Class may be over, but we have to get back to the building. What she did to you was only a warmup. She can't affect me or Karyn or anyone in her class, but she was still able to...."