Pedro felt pressure against his hands and looked down to see his already large endowment swelling out and getting darker. At the same time, there was a tingling in his ears and butt. The other sensations were alarming, but Pedro only had eyes for the changes going on between his legs. His penis thickened and the end got flatter, with heavy veins forming along the length. A heavy foreskin rose up and pulled his penis against his belly as formed into an animal sheath, and he could see the swinging orbs of his testicles as they swelled into black tangerines.
"What have you haaaaaawwwwwww! HEEEEEE-haawwwww!" Pedro clamped his hands over his mouth, which was protruding out way too far. Stumbling back, he tried to run but fell as his legs locked up. He caught himself on hands that were oddly numb, and was hit with a series of spasms that shook his whole body, each one making him feel thicker, heavier, larger. He screamed, but once again all that came from his mouth were brays of a jackass. When the strange sensations finally stopped, Alberto came over to stare at him. The boy looked shocked, and also smaller. It took a moment for Pedro to realize it was because he was bigger. Anger boiled up and Pedro lunged at Alberto with a bray of rage, his powerful muzzle open to bite. The old man shouted something else, and Pedro suddenly went still. He felt confused, the anger replaced with affection for this small human. No! It was his brother, not his... master? Pedro realized with horror that he had become a large donkey, and that he was starting to think like an animal as well.