"Okay," one Mary said to the other. "I probably want to keep going as much as you do. Can you guess which vial I'm thinking of using?"
"Well I'm actually in the mood to try the cow vial again.
"Yes! Wasn't it great? That udder--"
"And those hooves--"
"And that TAIL!" both Marys squealed in unison. They cracked up and then one reached for the cow vial.
"Bottoms up," she said. She tipped half of it into her mouth and handed the other half to her twin.
Both women felt the effects immediately. They exchanged looks of surprise, knowing that the change had taken them--her--all day before.
Their bellies started swelling, filling into fleshy udders. Both Marys rubbed and squeezed them in delight, reveling in the sensations. Then something strange happened.
Both their udders grew teats, but they were much longer than the ones Mary had before. These kept growing out, defying gravity, and reaching toward each other. Before they knew it, their teats had merged between them and formed four long tubes connecting their udders.
The tubes began pulling the Marys closer together. One Mary braced herself on the counter, but since the other had no close means of support, she was drawn right to her. When their udders were bumping into each other, they started squeezing together. Both Marys moaned at the intense bloated feeling, as if their bladders were being compressed. Then the skin between the udders seemed to melt away as the two converged to form one giant mass.
They looked at each other, their faces not a foot apart, both terrified at the bizarre changes that were occurring. Meanwhile, white and black fur sprouted on their legs, their feet formed into hooves, and tails shot out of their butts. None of these were noticed much, however, as the women were more concerned about the giant udder that now connected them.
"What the hell are we going to do?" one Mary asked. The other was at a loss for words.