"W-wait!" Dr. Jenkins pleaded desperately, finally breaking his silence. "I can explain... it's not what it looks li- urgh!" He tried to get to his feet, but the men from the pickup truck grabbed him, holding him still and forcing him back down to his knees. All Jenkins could do was watch as Lily approached him with a smug smile, syringe at the ready. She stuck the pointy needle into his neck, injecting the black fluid into his body.
Though the goons released him, Jenkins could already feel the serum surging through his bloodstream. He gasped and shivered, skin itching, heart racing. "W-w-what did you just do to me?!" He demanded, voice stuttering.
"Well, my sister's always loved cats." Serena chuckled. "We decided to go with something fitting..." Jenkins cried out as his body began to break out into fur, yellow hairs rapidly sprouting all over his body. As they thickened and spread everywhere, they became speckled with black spots... becoming quite typical of the average cheetah.
Jenkins saw his fur-covered fingers shortening, nails aching and sharpening before his eyes. He groaned and dropped to his hands and knees, feeling his palms grow rough and calloused against the office floor. Jenkins' bone structure was undergoing rapid changes, elbows locking up and disappearing, back cricking into a quadrupedal position, legs reforming into a cheetah's fast, powerful haunches...
"P-please... l-l-let... meeewwwwww..." His speech devolved into a cheetah's pitiful mews and growls. While the fur washed over his face, he felt his teeth sharpening, whiskers sprouting from his cheeks. A long, rope-like, spotted tail sprouted above his rear, and his heels rose off the ground, feet cricking and morphing into digitigrade paws. Jenkins' twitching ears slid up the sides of his head, and he let out a final cry of pain as his face stretched out into a blunt muzzle, nose turning black and wet and feline.
A cheetah stood where Dr. Jenkins one did, in the torn, unfitting remains of his clothing. As he tried to gauge his new body, overwhelmed by strange senses, he felt a tranquilizer dart hit him. The final thing he saw before slipping into unconsciousness was the sisters grinning down at him...