Ty realized he knew what he'd most like to turn into. He'd always found anthro characters fascinating, and wished it was possible to be like that. In particular, catgirls were really appealing to him. He felt like it'd be worth it- or even nice- to not be a girl to be a catgirl instead.
He focused on the form that he felt a longing for. It wasn't dissimilar to a human form in many ways, but it had a layer of fur covering the skin, ears which stood up from the head and were able to pick up subtler noises, perceptive glowing eyes, more lithe and flexible muscles so it could effectively run on all fours, sharp claws and fangs instead of human nails and teeth, and a long dexterous tail.
As Ty imagined these altered features, he saw and felt them emerge on his body before his eyes. His skin prickled all over as fur began to sprout across it, and his existing body hair seemed to meld with it. His vision and hearing amplified as they turned from primate to feline. His flesh rippled and slunk inwards due to his musculature gaining the ability to move in more ways and his form getting more petite.
He grinned and saw his teeth sharpen in his mouth, looking down to see his nails sharpen and narrow, retracting into his fingers and toes a little, awaiting the opportunity to extend and slash out. A pressure in the base of his spine was relieved as a true tailbone extended out from it, which he realized he could move fairly freely. Seeing himself like this was making something click in Ty's head: I'm an animal now, he realized.
Ty was so struck by how he had changed species, he almost forgot the fact he would also change sex- until his body reminded him quite vividly. He felt a twinge in his chest and saw soft flesh expanding and nipples poking out from his fur. A part of him considered having his body form more nipples, or even more tits, but figured he should get used to two breasts first. Considering how hot he found staring at his mammaries once they had formed, he decided this was the right move.
Another weird sensation emerged in his body further down and he looked down to see his manhood receding. His penis shrank inwards and became more and more sensitive as it slowly formed a clitoris, his testicles pulled up inside him and reformed into ovaries, and his scrotum unsealed to form a vagina. Ty's new sex clicked in her head as she finished changing- she realized she'd become female.
Ty lowered herself to all fours and sat in front of the mirror, grinning. She liked how her new body felt and looked, and how her new instincts were giving her all kinds of weird ideas. She wondered which to indulge first...