"Woof!" Mark frowned and tugged at the collar. It didn't feel tight, but something else was wrong - he felt fur on his neck! Butler kept slurping his face, tail wagging and ears perked up. Mark knew he should make the dog stop, get up and get away from whatever was going on, but it felt sorta nice. He liked Butler's smell, the feel of the dog's tongue... he blinked, feeling confused. Butler pressed close, pushing him flat on his back, and planted huge paws on either shoulder.
Lick. Lick. Lick. Mark giggled and started licking back. He felt really weird, but really good. Warm, safe, happy. The grass felt nice against his bare skin. There was a flicker of concern. SHouldn't there be clothing between him and the ground? He looked down, having to turn his head slightly because of a dark mass in front of his face. No, the mass WAS his face - his muzzle.
Butler moved back, allowing Mark to push up awkwardly. He was naked now, clothes crumbled away to dust. That was funny. Sow as the feeling he had when Butler started licking at his crotch. Mark watched, confused but curious, as the dog slurped at his growing erection. Only before he got a full boner, his penis started to shrink back. It was weird watching the big dog lick his maleness down like a candy cane, but Mark couldn't do anything but watch until all that was left was a small nub. His testicles were next, vanishing completely under Butler's tongue.
It was getting harder to keep himself sitting up - Mark realized his arms were pulling painfully in his shoulders. He lay back and then rolled onto his side, and then on his stomach. It was much easier to push up that way - Mark shook his head, then twisted around to look at himself. Tawny fur was spreading across his body, and the whole shape looked different. More like Butler's.
He was turning into a dog! The shock finally broke through and Mark whimpered. Why was he letting Butler change him into a Great Dane? He felt a strange heat and dampness in his rear - a Great Dane bitch! Butler was very excited now, and instead of licking, he looked like he was ready to mount what was rapidly becoming his new mate!
He could try shaking the big male off and getting away, but he was also curious about the change. Butler was erect, his pink shaft pushing out. Mark didn't have long to decide!