Panicking, Nick tried to dash out of the ring, but found that he couldn't go beyond the mushrooms. It was like there was a physical wall around the circle, even though there was only a strange green glow in the air. The mushrooms were glowing now, and the will-o'-the-wisps were brighter. Nick had never believed in fairy rings, but now there was this magical wall that kept him from leaving, and he was...shrinking!?
Yes, Nick was shrinking, and rapidly. Before long, he was struggling to find his way out of his own clothes, which had completely enveloped him. As he tried to make his way out of his own shirt, a thousand strange sensations assaulted him, but he paid them no heed. Finally, he thrashed his way out of the neck of the shirt, just in time to watch as the grass of the fairy ring poked its way through his clothes, tearing them the bits as the glow left the mushrooms.
Nick stood there in the ring, naked. He was seeing the mushrooms from a different perspective now, and guessed that he was about twice their size, or four inches tall. But he felt more different than just shrunk. He examined his body...
Maybe "he" wasn't the right pronoun anymore. The breasts were the first indication of that, and a quick check of Nick's private (or, given the lack of clothing, public) regions confirmed it. Nick was a girl. With, she noted, rich pink hair that came down to the top of her neck, a lovely figure, and four delicate dragonfly wings. Nick had become a fairy.