Sitting in the front seat of his mom's mini-van, Jeff squirms uncomfortably. His body felt constricted, and worst of all his cock felt like it was about to burst. It was constricted by his pants, and Jeff could easily see the outline of his erection. His mind kept drifting to horses, mares more specifically. And to his absolute disgust, he was getting so aroused.
Suddenly, Jeff felt something slip free of the back of his pants. Fearfully reaching behind him, Jeff nearly screamed when his fingers touched growth at the base of his tail bone. Delicate hair had grown from the end of it, and Jeff could feel it twitching every time he prodded it. He was growing a tail, a horse tail no doubt. But what he didn't know was that his changes weren't finished there. While he was busy poking his new appendage, fur slowly crept up his chest and down his stomach. It was a warm chocolate color, accented only by the white star that's developing on his forehead.
Still oblivious to his changes, Jeff's ears creep up to the top of his skull. Stretching until they're a good four or five inches long, Jeff feels this strange sensation that is his new ears rotating and flicking. Reaching his hands up, he can almost feel his stomach plummet when he touches soft ears. He yanks down the overhead mirror and sees his face, mid-transformation. Covered in brown hair, with that white patch, and the sides of his head devoid of ears. Atop his head, he has the beginnings of a true mane between his new ears.
"Put that down Jeff, your mane looks fine. Honestly, I don't know why you're so fussy about that. The mares aren't that picky." Jeff's mom said, putting the mirror back up. Jeff whirled around at his mom, surprised she didn't seem to think anything was out of the ordinary. Then he remembered that the Chronivac probably did that whole, "reality shift" thing again.
"Great. I'm probably turning into some sort of horse-man." he thought. Jeff didn't know if these changes were permanent, he sincerely hoped not, but he also didn't know how long it would be before he got back home. Worse, what if someone discovered his laptop and messed around with it.
A ripping sound distracted Jeff from his woes momentarily. Looking down, Jeff was only mildly surprised to see his pants had finally ripped. While he vaguely heard his mom berating him for trying to fit into pants, Jeff watched as his legs bulked up. New muscles and more of that brown hair grew. Running his hand over his shapely thighs and calves, Jeff felt like he could run a marathon. It was exhilarating. And then it wasn't, as his bones cracked and shifted around. Adopting a digitigrade stance while sitting in the front seat of a mini-van was NOT comfortable in the least.
Jeff had the urge to open the door and run. His legs felt like they were going to explode. In a way they did. His foot grew, also tearing through his shoes, and Jeff saw his new hooves. They stretched away from his ankles, which were now more like fetlocks, and turned to stumpy lumps. Then hard, thick, black keratin enveloped the ends until at last Jeff's hooves finished developing. His tail had slowly been snaking further and further out of his spine, until Jeff could see it wrapped around his waist. It flicked every now and then, almost as if to remind Jeff it was there.
His upper body then transformed, but much less violently. Only his muscles grew, to rather insane proportions for a teenager. Jeff, tearing his shirt off, thought he looked more like a body builder than a high schooler. His chest had to be about two feet wide, covered in brown horse hair nonetheless. His biceps bulged, veins appearing, and his forearms felt as hard as steel. Jeff was beginning to wonder when it was going to stop when his face started burning up. Touching his fur covered face with nervous hands (also covered in hair but thankfully still hand in every other way), Jeff felt something was wrong. His nose was too big, too round, and his cheekbones were virtually nonexistent. Instead he felt one long hard bone, and it kept getting longer. Until Jeff was running his hands along the length of his new muzzle. His nostrils flared, allowing him to breath in his own scent. And his own arousal.
He could literally smell how horny he was. His cock gave another primal twitch, but now it was free of the confides of his pants. Jeff was very much aware of the boner he was sporting, though it was really only half hard for a horse. His hand went to it, and his cock twitched again. Jeff knew he shouldn't, but the sudden weight in his balls combined with his growing arousal made it hard for him to think straight. He couldn't even remember why he was in his mom's van in the first place, let alone surrounded by shredded clothing.
"Come on Jeff, we're here. We can't keep Mr. Hanson waiting." his mom drew his attention, and boy Jeff wished she hadn't. Through her open door, Jeff caught a very faint, but potent whiff of something that causing his cock to flop out of his sheath and then grow painfully erect. Jeff's mind swam as the scent lingered in his larger nose. He let himself be drawn out of the van by it. His cock erect, pinned to his chest, Jeff's mom made some comment about how eager he was now that they'd arrived. But all Jeff could think about was finding the source of the scent and ravaging it. His instincts were too overwhelming and sudden.