Tail.: Monkey
"Well well!" Madame smirked. "It seems we are beginning on your true form with a fitting animal. Enjoy a monkey tail you ape of a boy!"
Tyler felt a sudden jolt at his rear. His eyes widdened as a pressure grew at the base of his spine. A prehensile appendage pushed it's way out, snaking. His mind was racing with fear.
"This bitch is turning me into an animal!!" He thought as the tail reached 2 1/2 feet. The growth seemed to slow as the rounded, very simian tail completed. Tyler could feel the new appendage, and without thinking, began to wave it around without touching it.
Then, a wave of ticklish hairs began to sprout from it. They are the same color at tyler's hair. The fur was prickly yet soft, and only grew enough to cover the tail, making it finally look like a monkey's tail.
"Let's give our subject a round of applause. What tail!" Madame announced as the audience clapped. "Now, Tyler, what'll it be next?"