It was the cardinal rule of gym use, and he knew it. Never drink unfamiliar supplement drinks. You don’t know what they’ll do to you. Yet, when he saw the Bullhead mass gainer bottle sitting unattended on the counter, he couldn’t help himself. It was calling to him. He even found the packaging strange, with its flimsy wrap of the silhouette of a muscular man with bull horns flexing. Nevertheless, the creamy, white drink went down smoothly. He was ready to hit the gym.

He was too busy pumping iron to notice that the drink had had some unexpected side effects. He didn’t even notice his nostrils flare out and become slits. He didn’t notice his ears tapering and pushing out from his head, growing darker by the minute. He didn’t notice as his fingers thickened, the tips hardening and darkening into hooves. He didn’t feel his formerly shaven face and body become covered in a thin, wiry fur. And he definitely didn’t notice the keratin and bone growths that were protruding from his head. Until he looked in the mirror.

“Holy fuck, dude!” he said to no one in particular. “Fucking look at me, man!” He reached out to touch his reflection, and as his hoof tapped on the glass mirror, he saw for himself how his hand now ended in a split cloven hoof. “That was some strange preworkout,” he muttered, flexing his hairy arms in the mirror. Just to be positive, he reached up to his horns, and sure enough, they were there. He looked at his cowish nose, how it had changed from the color of his flesh to a dull grey. He looked at his hooves, grateful he still had some amount of dexterity in them. He looked at his ears, which were no longer human - they had pulled away from his head and were now black in color with a thin dusting of fur. He was just grateful that his earring hadn't been a problem. “This is the weirdest feeling ever,” he said. “Like… I feel fuckin’ great!”

It took some getting used to, but once he got the hang of his new hooved hands and worked them around the dumbbells, he kept on with his workout. It was the greatest workout he’d ever had. Lifting weights with his new bovine strength was a feeling unlike anything he had experienced before. He even found that the more exercise he got, the happier and hornier it made him. By the time he was ready to go, he felt larger, stronger, and dumber than ever before. He turned to leave the gym… and ran straight into another gymbull. This guy was massive, standing at least a foot taller than him and with even thicker muscles. His horns, fur, and hooves even bigger than his. This guy even has a ropey tail swishing lazily behind him.

“So,” the gymbull said. “You’re the little calf who stole my Bullhead. C’mon now, we’re got a lot to show you.”

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First piece I've done in a while, hope y'all enjoy!