Zane would never be able to change himself back to his original teenage girl self, since wishes couldn't be reversed, but there were other things he could do with the stone. And they were all associated with revenge.
He smiled up at his two big sisters and said "I wish Marie was really gothic, even more than I used to be." Marie was always so girlie, so this would be a real nightmare for her.
Marie's eyes went wide with horror as she felt herself change. Her blond hair became black with blue highlights, her skin turned pale, her make-up turned black, piercings appeared in her ears, nose and lip, and then her clothes changed, becoming a black corset, black ripped miniskirt, black and white striped stockings and black knee-high buckled boots with 4-inch stacks.
"I can't believe you just did that to me!" Marie yelled.
"At least now there will still be a Goth girl in the family," Zane said, with a smile. Then he turned towards Jenna. "Now, for you I've got something really special in mind. I wish ..."
