Mark picks up the vial labeled "Unleash the Beast", featuring the silhouette of some ferocious creature. Sam smiles when he sees his boyfriend's choice. The two of them had been getting into Furries lately, so the fact that Mark chose something with animals was not surprising. Mark read the back label of the vial.
"Unleash the Beast within you! This formula analyzes your physical, mental, and emotional characteristics and transforms you into an anthropomorphic version of the animal which best represents you. Results vary by user. Taste: Salty. Duration: 24 hours."
"Well, here goes nothing," Mark says before downing the contents of the vial and replacing it to be refilled.
At first, nothing appear to happen. Sam remarks that it must have been some elaborate hoax and the cameras will come out anytime now. In reality, the formula is currently analyzing Mark and and choosing what he will become.
Soon enough, Mark feels warm as his body erupts in a carpet of fur. He races to remove his clothing to avoid damage while Sam enjoys the strip show. Mark's fingernails and toenails fall out to be replaced by sharp black claws and his teeth elongate into fierce fangs. The fur covering his body turns orange on his back and white on his front with back stripes randomly crossing and creating an elaborate, asynchronous pattern. His jaw pulls out into a muzzle and whisker spurt forth from his cheeks. His spine juts out of his back and forms his new tail while his ears move up to the top of his head and his eyes turn bright green. His body grows to eight feet tall and bulges out with muscle, making his ears brush the ceiling. A furry sheath encases his cock which has grown to a foot long and thick as a beer can while his balls enlarge to the size of grapefruits. When his transformation completes, he let's out a roar that shakes the house.
Sam stands in utter amazement at his boyfriend's new body. He can't believe the potions actually worked! He can barely ask Mark in a soft voice if he is okay.
"Okay?" he exclaims in a much deeper voice. "I've never felt better! Look at me! I'm amazing!"
"You got that right big boy!" Sam says after regaining his composure. He cups Mark's balls in both hands and nuzzles his furry chest. "Do you want me to join you?"
"I insist!"
Sam takes the vial and removes his clothes as well. His skin is covered by slate grey fur as he grows claws and his teeth sharpen. His face stretches out into a much longer snout than Mark's and his eyes turn a feral yellow. His tail is shorter and fluffier than his boyfriend's. He too bulges with muscles, but only grows to six feet tall. His equipment undergoes the same transformation as Mark's, but stops at a ten inch pole with orange-sized balls. Sam lets out a long howl and pants eagerly as he looks at his boyfriend.
"Hm, a tiger and a wolf," Mark observes. "Sexy."
"Now that we have the fur, let's make the beast with two backs."
"Oh, I plan on it," Mark smiles lustily. "But before that, is there anything else you want to change?"