Ryan's arm swung out to show him holding a hat as well. "...and there was this cool hat, too." He put it on his head and struck a pose. He didn't notice that there were slits on either side between the brim and the top of the hat.
The ripping sound from behind him diverted his attention from his head, though. The itching sensation that accompanied the sound caused him to reach back to scratch his butt. What he found there made him spin around to find something attached back there. No; not attached. It was a part of him, albeit a part new to him. Long, coarse hair cascaded from the torn opening in the pants, and a closer examination would've shown the cause of the itchiness, as the area around it began to bristle with a short coarse coat of hair.
Ryan had a tail. He looked behind himself, mute for the moment with wonderment. Growing a tail and fur distracted him from the other change taking place at the sides of his head, where his ears were growing pointed and taller, growing toward the slits in the side of the hat like plants seeking the sun. As the tips reached the slits and poked their way through, their growth exploded. Soon they had reached their full size and character, and they twitched and then swiveled toward the sound of Marcia's voice. Their twitching led Ryan to reach up and feel them with hands whose fingers had grown curiously short and stubby.
"You IDIOT!" Marcia cried out in irritation. "Didn't you wonder what that hole was for? You're turning into a horse!" But Ryan's dulling intellect did not see just what the problem was; he only knew that he felt really strong and healthy and good, and he smiled as the next thing to grow larger and stronger was the swelling in the front of his pants.