Rob tries to resist, but it's no use. With now even more of the vial's contents coursing into his digestive tract, his changes begin to accelerate. His chest and neck thicken considerably, as the black hairs all over his body multiply until he's got a thin coat of fur. His nostrils flare and broaden, until they become snoutlike in form and horns slowly grow from his forehead, curling out evenly.
His feet, slimming and taking on hooflike formation, slip out of his shoes and a long tail slides from his backside.
And still, Mary presses the kiss, even as Rob continues to grow larger and larger, until he is more massive than she and strong enough to move her. He places his broad, hooflike hands on her waist and lifts her off of him, standing up and examining himself in shock.
"Dammit, Mary," his deep, baritone voice grumbles. "This isn't right."
"I know. It's so so bad of me." Mary pouts as she sits down on the couch, exaggerating a frown at him. "So you had best punish me. Make me into a good little cow."
"Oh, God, this isn't happening."
"But it is. Isn't it great? You look so hot, by the way. Take it off. Those pants look awfully tight."
"You're relentless."
"And you're a bull. What's your point?"
"I'm a MARRIED bull - er... man. I'm a married man, dammit."
"And now you're not even the same species as your wife. What a shame. Give me what I want, just once, and I'll give you the cure and you can go back to your wife and I'll never bother you again. Promise."