A sly grin came across Jess' face. "'Goes well with cats,' hmm?" she echoed. Mary's cat ears pointed straight up, indicating the newly-made catgirl's attempt to guess what Jess was getting at. She watched her friend pluck a vial out of the box, but she wasn't able to see the label before Jess put her hand over it. "Nuh-uh," Jess wagged a finger. "You'll see what it is soon enough." She pulled off the top of the vial and drank almost half of the liquid inside.
Rumbling inside Jess' stomach caused her to let out a surprised "Ooh." She giggled at Mary and rubbed her belly...which seemed to be growing. Jess pulled her hand away in a flash. Mary looked closer and saw it wasn't her belly expanding, it was a part of her just underneath.
Her pupils contracted into the thinest of slits as her eyelids widened. Jess had chosen the first vial Mary had used: The cow vial! Even now her udder was slowly pushing up Jess' top and straining the waist of her pants. Jess fumbled with the hidden zipper and finally managed to pull her pants down, making her growing udder flop down between her legs. "Oh, that is MUCH better," Jess said in a weak voice. Mary could tell from her face that even though Jess was expecting a real change, she was still coping with the surreality of the situation.
Something was moving behind Jess. Moving sideways to get a better look, Mary saw what it was. "Nice tail, Jess," she complimented.
Jess snapped her head around and grasped her black and white tail with both hands. She tried moving it voluntarily and watched it give feeble jerking motions within her grasp. It was tipped in a thick black tuft that matched the hair on her head. "This is amazing," Jess said. "I can't believe...I've actually got a tail!"
"And an udder," Mary reminded her, pointing a claw at the fully-formed cow udder sagging from below Jess' stomach. Jess returned her gaze to it and saw it had swelled with a fair amount of milk, now about the size of a soccer ball. She had to stand with her legs at a slight distance in order to let it fall freely. Jess stepped out of her pants, leaving them on the floor and sitting down on Mary's bed.
Mary continued observing her friend as her orange tail swished behind her. Two small horns had begun their escape from Jess' hairline, and it looked like her ears were beginning to point outward. Jess held her udder with both hands, feeling their weight and the tenderness of the pink flesh.
"So," Jess smiled. "You thirsty?"