Mary knew exercise was the key to getting her old body back, and she thought of animals that could handle a strenuous workout. A running cheetah popped into her mind, and she knew it was worth a shot. She found the cheetah vial and took several swigs.
Within minutes, her legs were covered in yellow spotted fur, and a long tail had grown from her butt. Some fur had started to creep up to her chest, but for the most part her upper body remained the same, just as the cow vial had first affected her. Her legs were perfect hindquarters of the fastest animal on Earth.
She threw on whatever shorts would fit on her large hips and stretched as best she could given her modest bulk. Then she started her long jog.