Karyn gripped the stone tightly as she said, "I wish I knew what my last few wishes changed about reality." And, like magic, she knew: Humanity in general was a race of changelings, going through a first involuntary, week-long transformation, usually some time during puberty, though some did so long before and some long after. What they changed into was partly random, but partly determined by their heritage; some families had many of one type, sometimes not. That first transformation also often determined the general scope of what was later possible for that person.
"Hmm..." Karyn mumbled. "This is really interesting. I wish I knew what Jon's abilities would be and why." The knowledge entered her head not with a rush, but as if it were always there. He would be able to turn into living dresses of most sizes, because his father's side of the family had that tendency. She giggled. "I wonder if he'll lend himself to me sometime. It'd save a lot on clothes."
She walked home, only a block away, putting the rock in her pocket and heading right up to her room. This wish was already so much fun. Karyn thought about wishing to find out what she'd be, but she decided she'd rather be surprised.