Jess thought it would be a funny joke to take the dog vial now that Mary had taken the cat. After all, they were friends. She wasn't really going to attack her or anything.
So, she drank over half of the vial, as Mary had with hers. It tasted disgusting, but she managed to swallow it.
The first thing she noticed was the prickling sensation of fur growing on her body. She watched as hairs pushed out on her arms. They were colored pure white on her forearms and just before they got to her elbow they changed to a rust brown. Her fingers thickened and her nails darkened into sharp claws.
Pain in her feet told her she'd better remove her shoes and socks. Once she did, she saw that her feet had shortened a bit and had short toes with thick claws much like her hands. White fur was growing around her ankles.
She searched the room and found Mary's vanity mirror. She watched as her ears moved to the top of her head, growing bigger and forming points. The skin was so thin the tips flopped over just a bit.
Her nose flattened and turned wet and black. Her face stretched out into a half- muzzle somewhat longer than Mary's, but not nearly as long as a true dog's. Rust fur grew across her face, except for a thin line of white that ran down between her eyes and ended at her nose. The fur just underneath her chin and down the front of her neck was white as well. She guessed that the white fur carried all the way down her chest as it did on Mary. Her irises darkened until they were almost as black as her pupils, and her teeth grew into canine fangs.
She saw that she was losing altitude, as she watched the mirror grow a bit. Her top loosened up and her pants began to slip.
She felt a sharp pain in her rear, and realizing she was growing a tail, she quickly unfastened her pants and took them off. Now she was staring at a bushy collie's tail, rust red with a large bit of white at the tip.
A bulging sensation in her chest alerted her to four new breasts growing in, and she pulled up her blue sleeveless top to take a look. Sure enough, her chest was covered in white fur, and two new sets of breasts were filling up right underneath her original pair. Her back had gained its coat of rust-colored fur, and her black hair barely retracted at all, which was an exception to the rule as Mary's shortened quite a bit. It still fell halfway down her back, however its color was now lightening to match the rusty red of her fur.
Now that the transformation was completed, she looked at her friend for a reaction. Mary was still shorter than her, though by less now. Mary was around four and a half feet now, so Jess figured she had only shrunk to five feet. Mary's eyes were wide with terror, and Jess could see her shaking.
"I told you to pick something that went well with cats," she stammered.
"Oh, relax," Jess reassured. "It's still me, your best friend. I'm not going to tear into you just because I'm a dog." It was true that Jess had no intention of chasing Mary around, but what she didn't want to tell her friend that she was already feeling the alien canine instincts creeping around in her brain. And one of them was telling her that Mary was far from a friend.