Ty looked at the pair. "You're about to get a lot closer. And hairier."
The father suddenly dropped to the ground, his clothes ripping. He reached to hide his equipment from his son, but was soon distracted by a pain on the end of his spine. Vertebrae were being added, forming a tail that began to sprout hair.
"What are you doing to him?" Asked Todd, unable to keep his eyes off of his father as he changed.
"Giving him a form I like better. And you will, too, pretty soon."
Dean was growing, his muscular body putting on extra muscle and a thin layer of fat as hair started to grow. He was forced to move his hand from his groin as his fingers shortened, thumbs stretching upwards to form dew claws on his new paws. His legs shortened, the heel moving upward and leaving him standing on his toes. His ribs shifted, becoming more barrel chested. Todd watched in morbid fascination as his father's face started pushing out into a muzzle, no longer resembling a human.
The last change that Dean went through was to his junk. His balls started to swell, his scrotum tightening and causing him to get aroused despite himself. They moved back towards his anus before stopping their growth, now the size of softballs. His dick was next, the foreskin attaching itself to his stomack and growing fur before starting to turn a deep red and grow obscenely. The tip became pointed and the shaft grew thicker, nearly as thick as a soda can. The length was at least ten inches, and his knot had yet to come out of his new sheath.
Todd couldn't help but stare. Ty made Todd's clothes disappear, who hardly noticed in his reverie. Dean was very aroused, smelling something he couldn't put a finger on before looking at his son. His arousal was focused on Todd, whl was still too focused on his father's changes to realize what he was doing as he walked behing him. Suddenly, Todd felt his father's wet nose on his anus, Dean's tongue wetting and lubricating the area. Todd moaned, falling onto all fours without a thought, and his father jumped up, his forelegs hooked around Todd's waist as his doggy dick probed for his son's hole. The tip drooled, coating Todd in more natural lubricant as the tip finally slipped in. Dean thrust, illiciting a cry of pain from Todd as the first inch of his thick dick entered his son.
"Let me help with your little problem," Ty said, and caused Todd's anus to become much more elastic, causing him to moan at the change from pain to pleasure. With less resistance, Dean thrust again, getting into a rhythm that soon had his dick buried up to the knot in his son. He pressed forward, causing a cry of pleasure from Todd before the knot slipped inside. Dean then sped up his thrusts, nearing climax. He burst, filling his son with the stuff that had made him. None could escape past Dean's knot, and it kept filling Todd more and more, his stomach bulging like he was pregnant. The father and son were stuck together for another half an hour, Ty watching, before the knot was small enough for Dean to slip out. None of the seed spilled out as Todd's anus closed up as soon as it wss empty.