Jess, the mare, watched Mary as she pulled out one vial. She hesitated, breathing in a long breath. Mary took out another vial. Jess wondered if Mary was undecided. Jess tossed her silky mane in impatience and snorted. Mary glanced over at her changed friend, winked and took out a third vial.
Mary gestured with her free hand for Jess to back up and give her room. Taking the three vials, Mary walked out of the room. "I'll be right back," she giggled.
A minute later, Mary returned with a tall glass which she set on her nightstand. Jess, curious to see what vials Mary had picked out edged closer and lowered her head over Mary's shoulder.
"Hey, I'll have none of that!" Mary pushed Jess's head away and Jess dejectedly walked back to her corner to watch. Satisfied that Jess wasn't going to see what vials she'd picked, Mary began her work. She opened two of the vials and dumped all of their contents in the glass. Next, she opened the third vial and put a quarter of the liquid in the glass. Mary took the glass and swished the contents slightly. The differently colored liquids melded together to become a rainbow of color.
Mary turned to Jess and quickly gulped down the magical contents of the glass. "Jess, I just want you to know that I can't help myself. You're such so cute as a horse, as a mare. But, I'll bet you'll enjoy this just as much as I will." Mary giggled and suddenly belched. Her hand shot to her mouth as she blushed.
Mary let out another burp and sat down awkwardly on her bed. Jess watched intently as Mary began her transformation into who knew what. Jess for sure didn't. Though she was a little curious and rather scared. Mary leaned back onto her pillows, her clothing became tighter. Jess could see that Mary's shirt stretch was her friend swelled with growth. She groaned and ran her hands over her taut chest.
A loud tear brought Mary's shirt to an end. It fell to the ground and Mary continued to run her hands over her transforming body. Her once full and round breasts shrank like deflating balloons and in no time were gone completely. Jess watched in rapt attention as a large bulge grew in Mary's pants. Like her shirt, it too grew taut and with a sudden bang, ripped apart. Jess's eyes bulged at what she saw. Mary wasn't a girl anymore. Far from it. Her friend now sported a small penis and sack. Mary moaned and her roaming hands crept down to her new equipment and explored them. In her hands, they stiffened and swelled. With each passing second, it grew in width and length. Mary caressed himself and seemed to be enjoying it immensely.
Jess couldn't tear her gaze away from Mary's transforming body. His new equipment wasn't done quite yet, either. The penis rose parallel to his chest and attached to his belly, forming a sheath. Dark brown fur spread out from the sheath and began to cover Mary's body. Jess's attention changed from the new maleness of her friend to the changes taking place in her face. Mary's ears had moved to the top of his head and kept on growing, lengthening. Jess knew instantly what kind of ears those where. She knew what Mary was becoming.
"Hee...Hawww!" Mary bellowed, adjusting to a new muzzle. Large lips grew to hold large, comical teeth. Mary shifted on the bed, his weight making it creak under him. He stumbled off and fell to all fours on the floor. Mary's arms lengthened and grew hooves. His thighs flattened and grew hooves as well. A long, rope-like tail sprouted from the near-complete donkey and snaked down behind him, a tuft of brown fur popping out on the end.
While Jess had noticed that Mary had transformed herself into a donkey, she hadn't realized that he was also growing bigger than a normal donkey. Big enough, in fact, to be larger than herself. Jess quivered, her flanks shivering in the sudden realization of what Mary had meant before.
A huge, male donkey shook his head and turned toward Jess. This was her friend, Mary, her best friend. Things were becoming very strange, surreal. Everything outside, everything in Jess's life felt a lifetime away. She was focused on her and her friend's new bodies.