Mary was caressing Rob, pressing and massaging his wonderfully warm rubber body. She giggled which ended up as a moo when Rob unconsciously started to purr.
"You know, Rob, I've tried being an animal, but you've tried being a rubber toy! I think I ought to see what that is like." Mary rubbed Rob's pert ears.
"It's wonderful," Rob purred, "very different. You're empty, but at the same time, you're full. You're body is shaped so that you're not flat, but round, plump. But, then, feeling yourself swell...Oh Mary, I've never felt anything like it.!"
Mary, convinced now to try the new experience, found the rubber vial and drank all of the contents. The effects were immediate. The shiver ran over her half-cow body as it changed to rubber. Mary mooed giddily as her once weighty udder snapped to pertness. Her teats stood straight out from her rigidly. She flicked a could and shivered in pleasure as they snapped back into place. The rest of her rubberized and became air-filled and taut. Her tail, her ears were plump enough to be rigid and with give at the same time.
A silkily rubberized cowgirl stood in front of Rob, running her half-hooves over her strange new body, mooing contentedly.