"The box! Quickly! " said Mara. "The vials inside can change you! Find the human one and give it to her."
Amy grunted and winced, trying to will herself to remain human. John ran to the box, and quickly returned with the "Female" vial.
"Not that one you fool! The one that says "human". Can't you read?" said Mara angrily, as she tried to comfort Amy.
John blushed and turned, tripping on the carpet. He spilled the contents of the vial all over himself. John didn't bother to dry himself off. He knew his sister didn't have much time. He returned with the Human vial, and Amy quickly drank it. John watched in fascination as Amy's transformation into a fairy suddenly stopped. Slowly, she began to grow, stretching out of her small fairy clothes. Her skin lost its luminescence, and the fairy dust began to disappear. John was so entranced by Amy's transformation that he failed to notice his own. His body tingled, but he just assumed it was an allergic reaction to whatever was in the vial. He absently scratched his skin as it grew softer, and he lost all body hair.
Amy grunted as she finished her transformation back into a little girl. She was a little embarrassed by her nudity, but Mara quickly found a towel for her to wear.
"Thanks, brother, " said Amy, as she looked up at John. Suddenly, she started to giggle, and covered her mouth with her hand. Mara looked at him too, and began to laugh.
"What's so funny?" said John. He voice sounded strange. Higher and squeakier. His voice was amusing to the girls too, and they began to laugh even harder. John crossed his arms angrily, and that was when he felt them. Two small mounds protruding from his chest. He looked down his shirt and saw two large puffy nipples. He reached down and felt his groin, confirming his fear. He was now a girl!
"I guess I should have said thanks, sister, " said Amy with a laugh.