As if the revelation that you have, overnight, become a rather large-breasted sixteen-year-old girl wasn't enough, the mirror reveals that even more changes have taken place. Instead of normal human ears, yours are thin and triangular, located at the top of your head. They are covered in light calico fur; quite clearly cat-ears, though proportionally larger than a real cat's.
Moreover, you feel something at the base of your spine. Reaching behind your now-curvy behind, you fish out a tail, also covered in calico fur. Like the ears, it's proportionally larger than a real cat's; about three feet long and an inch thick at the base. Looking at the hand that holds it, you notice that where a normal girl would have fingernails, you have retractable claws.
As you stare in shock at your new female and feline features, your jaw drops in shock and amazement, revealing that your canine teeth have become fangs. The overall effect would be adorable on anyone else, but you find it less "cute" and more "terrifying" when you consider that the creature in the mirror, a buxom teenage cat-girl, is you.
What could have done this? you wonder. As you ponder this, you feel something dangling between your new breasts. Reaching into your...cleavage, you find the necklace you obtained yesterday at the carnival. You suddenly notice anew what's written on it: "Kitten."