You point the key at Keith and push the unlock button.
I'm not sure how it works, but I guess I can't make it any worse, you think as Keith begins to change again.
You hear Keith whinny, as his back begins to crack. He stumbles a little, as his front hooves begin to change. His front hooves split, forming three thick fingers ending in a dark black nails. His legs shift, and he slowly stands on his rear hooves. His swollen abdomen deflates, becoming flat with washboard abs. His barrel chest contracts a little. It is still broad and wide, but begins to look more human. His snout recedes a little, and his whinnies become recognizable human words and grunts. You expect him to complete his transformation into a human, but the changes suddenly stop. Keith is left as some kind of hybrid of man and animal, an anthromorphic horse.
Keith looks at his body in shock, twisting around to see the front and back of his body. You stare at him in awed silence.
"What the hell, man? Why didn't you change me back? " says Keith. His voice is much deeper, with a very manly baritone.
"I tried. I am not sure how it works. But hey - at least you can talk now. And you look more human. We can probably just tell people it is a costume, " you say.
Keith storms over to you, his large hooves loudly clomping in the street.
"Give me that! " says Keith angrily, as he grabs the key from you. Standing close to you, you realize how intimidating Keith now seems. He is easily 8 feet tall, with an athletic frame covered with lean muscle. He has to weigh a ton! You decide it is better to let him try to fix himself. But he stares at the device with confusion.
You wait patiently for him to give up, and return the device to you. Keith's tail suddenly slaps his thigh, knocking down a flying insect.
You can't help but laugh. "Maybe you aren't as human as I thought!" you say, and immediately regret it.
Keith glares at you angrily. "You think this is funny? Let's see how you like it!" says Keith, as he points the key at you and presses the unlock button.
You feel yourself beginning to change. The ground drops away as you grow taller. Your pants groan as your thighs grow larger and begin to tear them at the seams. Your shirt feels tight, too, and it begins to rip as well. Your shoes slip off as your feet become longer and slimmer, shifting into hooves. Grey fur begins to sprout all across your body. You look at your hands. The fur developing there is dark black. Your fingers merge, becoming three thick digits, ending in dark nails.
Oh, well, you think. At least I am becoming an anthromorphic horse, instead of a full horse. Keith doesn't look that bad. In fact, he looks pretty good.
You find yourself admiring his body. The broad shoulders, the powerful muscles, the generous endowment. You find yourself getting excited thinking about Keith's body and look forward to your change. A sudden tear in your shirt catches your attention. You look down to see two small buds developing on your chest. They slowly swell, growing larger and more sensitive. The nipples above the tissue grows larger, and the areola expand around the stretching tissue. You hold the tissue in your hands, trying to contain their growth. The breasts feel good as you feel the flesh expand beneath your hands. They begin to grow more rapidly, quickly reaching a C cup, then a D cup, and beyond. Soon, you can no longer hold them.
"What the hell?" you say. Your voice cracks, squeaky and slightly higher in pitch. You notice Keith staring at your groin with interest.
You look down and see that your dick is thicker, but much shorter. It continues to become more compact as you watch. Your testicles are larger, too. But your scrotum is wrapped tightly around them. The skin around your scrotum is dark black and very thick. You reach down to touch it, and are surprised by how sensitive it is. Your scrotum seems to be shrinking, retreating into your body. It drags your testicles with it, pulling them into your body, leaving behind a hole lined by the thick ridges of your residual black scrotal tissue. As your penis shrinks into this hole, forming a large clit, you realize this is your new horse vagina.
Finally the changes are over. You cannot deny what has happened. You have become an anthro-horse, just like Keith. But a mare, instead of a stallion.
"Well, well. What have we here? A pretty little filly?" said Keith. You see his horse cock twitch a little, just the tip poking out of the sheath a little bit.
"Don't even think about it! Why did you do that? What were you thinking?" you say angrily, trying to cover you exposed breasts and genitals.
"Relax! I just wanted to give you a little extra motivation to figure out how to get this thing to work. Not so funny now, is it?" says Keith, crossing his arms.
"I was working on it! You didn't need to ... to .... well, to do this? Give me that!" you say stomping over to Keith. This time it is your hooves that thunder on the ground. You realize that you are almost as tall as Keith now, and nearly as strong. He isn't quite as intimidating as he was before.
"Here, take it. And good luck, " says Keith, as he hands the key to you. You struggle to look at the key, and keep yourself covered.
Keith chuckles. "I don't think you need to hide anything. We're all friends here. And if anyone else sees you, they will just think it is a costume, right?"
You sigh and drop your hands. It was impossible to use the key, and keep everything concealed with your hands. Strangely, your are not that disturbed by your nudity. But the look on Keith's face as he continues to stare at your new body is disturbing. More disturbing are the odd feelings of excitement you feel when you look at his nude body, especially his large cock.