Suddenly, David grew a bit muscle, and a short stumpy tail popped out from his behind, just above his butt.
"Arrk!" David exclaimed, his voice starting to catch. "What's this?!"
He took one look behind him and SCREAMED. "I'VE GROWN A TAIL!!!!!!"
"Holy cow." Dennis said, staring at his brother like a deer caught in a car's headlights. "You're really changing, aren't you!"
Suddenly, David doubled over in pain, collapsing to his hands and knees. Then, on his back, he grew short stumpy brown spines, like those on a dragon, but slightly bigger.
David grunted and screamed as they grew; the change wasn't painless.
Eventually managing to roll over on his back, he was able to see his dick, or rather, what was left of it, anyway.
It was now nothing more than a stub, the last of his holdout between manhood and humanness.
holy shit!