The was a knock on the front door, making Jen jump. She ran downstairs, trying to think of a way to get out of what was going to happen to her, but as soon as she opened the front door her memory of the last few minutes went completely blank. She looked outside to check who it was, not surprised to see Greg standing there. Sometimes her boyfriend annoyed her, when she took too long getting ready he would come to the front door instead of waiting outside like he should. Sometimes she even wondered why she dated him, he wasn't that great in the sack, but the head cheerleader had to have the hottest looking guy on the football team, right? She often wondered how someone that good looking, and hung like he was just couldn't perform.
"Oh, Greg! I'm almost ready." She turned and walked back to the stairs as Greg came inside and shut the door behind him. Suddenly Jen felt a cramp in her middle, what was going on? She felt like she should know, but it kept slipping through her fingers. Her body felt like it was on fire, everything about her was growing, stretching. With the sudden sound of ripping fabric her usually tight clothes fell off. She looked down at herself, her entire body was still growing, her shoulders were getting wider, her chest pushing outwards. But her breasts, they were slowly shrinking away, the nipples becoming smaller, even as her chest swelled with muscle. Soon her chest looked like that of a male body builder, no longer the petite frame with large firm breasts she used to have. Her arms were also swelling with muscle, her biceps growing into boulders, only out sized by her delts. She turned, wanting to call to Greg for help, but when she saw him he was staring at her, stunned, and groping himself through the fabric of his jeans. He was getting off on this, off her turning into a... guy. Then it all fell into place, no wonder he never was good in bed, he prefered..
Her train of thought was interrupted as itching broke out all over her torso, especially across her new pecs. Dark curly brown hair began to push itself out, a trail going right up her abs to the thick growing forest on her chest. The feeling of her head being clamped in a vice signaled the next set of changes. She reached up, feeling her delicate face with her now large meaty hands. But it wasn't that delicate anymore, she had a strong chin and square jaw, a thick brow and what felt like stubble growing in all along the jaw. But she stopped as she felt her ears, they weren't human, they had grown to points, the backs covered in fine hair, what was she becoming?
She looked down at herself, she looked like a freak with her male upper body and her female lower one. That was until he knees started jerking. Her legs were changing, the joints rearranging themselves at odd angles. Her toes began to fuse together into hooves. She felt a strange sensation in her vagina, like someone had stuck their hand up there, grabbed something and yanked. From between her legs dropped two massive balls the things hanging practically to her knees, but her legs were growing longer as well, and thicker. Short dark brown hair sprouted all over her altered legs, except near her two hooves, where it grew in long and white. A tug on her backside announced the sudden growth of of a tail, which she felt with her hand. Then it struck her, her legs looked like a horse's hind legs, as if to confirm her suspicion, her clit migrated up her crotch, suddenly swelling and pushing outwards. The form it was taking wasn't human, she had seen this before, he father had bought her a horse and she had seen stallions at the stables. It was a horse's cock, and it was huge. In fact her whole horse part was massive, it looked like one of those clydesdales she had seen. The cock didn't stop growing until the tip of it brushed the floor, sending shivers through her body.
There was a sudden odd sensation on either side of her stomach. Two nubs had suddenly appeared, and they were growing hard and dark, looking like another set of hooves. The distance between her abs and her crotch seemed to stretch, but soon she dropped down on a pair of new horse's front legs to match the hind ones. A sheath was forming, pulling her cock up against her horse half, even as he backside pushed farther and farther behind her. Centaur, that's what she was. Then from between her front legs there was another curious tugging sensation. Another pair of balls dropped, not as large as the ones that were now behind her were, but still bigger than any human one's she had seen. If her hind ones were watermelons, these were grapefruit. Another cock began to grow above the new pair of balls, this one distinctly human in appearance, though once again, much too large. She had to guess it was two feet long, and still soft. An itch down her back she knew was a mane growing in from the top of her head to the base of her human back. She couldn't believe it, a draft horse for a lower body, and huge muscled body builder for an upper one, and of all things two gigantic cocks.
She looked at Greg who had been quiet this whole time, he was leaning against the wall, his hand down his pants and a growing wet patch covering his entire crotch. She wanted to yell at him, call him a freak for getting off on this, but as she opened her mouth a deep resonating baritone came from her. "Like what you see human?" Her mind was being slowly replaced by that of the centaur, images of ravishing Greg filling her mind. "How about you come over here where you can better appreciate me?"