He's on his way to school, trying to ignore all the new things he was sensing. He had been starting to get used to his claws... well, as much as could be expected. Now this. His furry ears were flopping around the sides of his head in the breeze. He had DOG ears and a muzzle! How does a person deal with that, except denial?
He just kept his head straight forward, pedaling his bike silently, trying to ignore all the new sensations. And there were a lot of them. He could smell everything... everything! As he passed each house, he knew what each person in every family was having for breakfast. He could detect every rodent burrowing in the grass. He could even tell which trees the neighborhood dogs had visited recently. Part of him was deeply tempted to stop and take another whiff, but that part was deeply suppressed. He just kept pedaling.
His ears were harder to ignore. He could hear people talking and dogs barking that could have been blocks away. Someone blew a dog whistle trying to retrieve their dog, and he winced. He never realized just how noticeable a sound that was to a dog; he immediately tried to forget the incident and just kept pedaling. His ears were floppy and movable, and they jumped or twitched at nearly every sound. He hurried forward.
Color vision was returning slightly. He could now see that the grass had a different visual quality from the sky. The violets had the same look as the sky... both were bluish. He was sort of relieved by this. "See?" he thought. "My colorblindness is passing. It was probably all in my head anyway." Unfortunately, he still couldn't see that the grass was a different color from roses, bricks, or even dandelions. He'd learned in school that dogs are red-green colorblind, but he chose not to think of this just now.
Soon, another feeling that was hard to ignore became impossible. It was a tingling feeling at the base of his spine, and it was becoming a pulsing throb. "I just slept on my back the wrong way," he thought. Finally, when he was almost to school, it became an unbearable pressure as a stiff growth jutted into the back of his pants. He moaned in pain and had to dismount from his bike. Getting into a standing position helped for a moment, but the pain got worse and he whined pitifully. Like it or not, he had to acknowledge this new change. He bent forward and tried to pull he pants down in the back. At last there was a wave of relief as something long flexed free over the top of the pants.
He sighed and started twisting in circles a little bit, trying to get a better look at his new TAIL. There it was, shaggy fur hanging from it, just like the tails he had seen on countless canines everywhere. And he could swing it around at will, just like they could. It was yet another new feeling chipping away at his denial. He reached back and touched it with a clawed hand, held the thing up, and quietly cursed.
Greg released his tail and stood up straight just to see a familiar kid also on the way to school. There was no question that she had witnessed the change as she backed away and ran away toward the school. Greg, filled with embarrassment, blushed under his fur and drooped his ears and tail like a dog would.