"I should have known," Mary said. "You're always talking about how you love cats."
"Yeah," Jess said, a bit shy, but sounding excited to see what kind of change would happen."
"I'll drink over half of it, so you can see a big change, though I still want to be partly human," she explained. "You're about to see what this stuff can really do." Mary uncorked the vial and put it to her lips. She emptied a bit more than half of the gooey liquid into her mouth and swallowed. It felt oddly rough on her tongue going down. She put the cork back in the vial and handed it back to Jess, who watched Mary's body intently.
The first thing Mary felt was a tingly sensation flow over her skin, leaving a warmth behind. A gasp from Jess told her the first change was apparent. Mary raised an arm to see that it was quickly being covered by orange fur. Her fingernails grew longer and curved slightly, forming claws. Looking at her bare feet, she could see her toenails doing the same thing. The fur on both her feet and hands was white as opposed to the orange which covered the rest of her.
Then a building pressure in her pants began to bother her. Guessing what it could be, she hastened to remove them. Slipping them off her legs, a growing tail was uncovered. It hung lazily from her lower back as it lengthened to reach the floor. When it was fully grown, it was four feet long and covered with orange fur. Its end, however, was tipped in white fur much like her paws. She blushed a bit when she realized she was now showing off her pink undies to her friend.
Mary looked back at Jess, wondering what she was thinking about all this. Jess's face was locked in a look of intense wonder, both of her hands clutching the cat vial firmly. That's when Mary noticed she was no longer at eye level with Jess. She had begun shrinking to the size of a cat.
The next tingling Mary felt was from her ears. She could feel them gliding through her hair, rising toward the top of her head. They expanded and formed a triangular shape, also getting covered in fur. The fur spread across Mary's face as her eyes turned yellow and her pupils reshaped into vertical slits. Her nose retained its pinkish skin color, but grew out slightly as her jaw inched outward into the faintest of muzzles. Her teeth ached as they thinned and grew into sharp fangs. Her tongue budded into a rough sandpaper texture. Small whiskers poked out of her cheeks and grew two or three inches.
A rubbing on the back of her shoulders alerted Mary to a change in her hair. She groped for the strands, which originally had hung down to her butt. Now her locks were retreating back into their follicles. They didn't disappear completely, however, as Mary still had several inches of blond hair left, giving her a shorter--but not any less attractive-- cut.
Then a pressure in her chest caused her to look down. Her shirt was a bit larger now, as she had shrank a couple of sizes. Since before it only came down to her midriff, it now came to her waist. The short sleeves looked like they could almost cover her elbows.
The pressure continued to build, and now it felt like it was just above her stomach. She lifted up her shirt, where she could see her bra was holding a slightly smaller set of breasts than it was designed for. However, underneath that, she could detect four small mounds forming lower on her chest. As they inflated, a dark spot formed in the center of each one, and Mary realized that she was growing two more pairs of breasts. The tits grew out of the dark spots, and each breast grew to match the size of her others. They were the same proportion to Mary's body as they had been, which thanks to the female vial she had taken earlier, was impressive. She noticed that from her top breasts to her crotch, her fur was pure white.
Shrugging her shoulders, Mary removed her bra and threw it on the floor with her pants. She saw no point in wearing a bra for only two out of six breasts, especially when they had gotten smaller along with the rest of her body and couldn't fill the cups anyway.
The transformation finished, and the tingling sensation dissipated from Mary's body. The catgirl stretched in her oversized t-shirt, rubbing her paws against her fluffy fur and practicing her purring sound. Jess walked a circle around the catgirl, who was now around four and a half feet tall.
"That's amazing," Jess cooed. "You're adorable!" She watched Mary's tail swish about her legs.
"Yeah, and I didn't even expect six breasts," Mary admitted. She thought back to when she had a cow's udder, and the sensations she had felt. She began rubbing one of her newly-formed breasts unconsciously through her shirt.
"So you would have been a full cat if you had finished the vial?" Jess quizzed, noting the vial in her hands had magically refilled itself just as Mary had said.
"Yeah, of course then I wouldn't be able to talk to you or anything," Mary replied. "So, do you want to try a vial now? The cat one?"