It always started as a dull tingling, almost like an itch, that slowly spread across her body. Then the itching subtly evolved into a mild burning sensation. Not a painful burning sensation, but more like the burn an athlete would feel deep in their muscles after a really hard workout.
Then the changes began.
Bones stretched, limbs grew longer, muscles puffed up like they were inflated with air. But they were definitely not filled with air. Janet could feel the lumps of hard muscle underneath her skin getting ever larger. As her body expanded, the leotard no longer felt quite so loose. It was getting snug as it pulled tightly across her growing body. Maybe a little too snug. She made a mental note to let it out a little before her next adventure.
Then the hard part began.
Janet's skin began to get thicker and tougher, with a leathery texture. Cracks began to appear between plaques rising across her skin. The itching was maddening, but Janet knew scratching would offer no relief. The long claws slowly stretching from the tips of her fingers would only damage her skin if she tried.
Janet quickly reached behind her body and guided the small tail growing from her sacrum through the hole in the back of the leotard. She had learned the hard way that she needed to do that as soon as possible. During one of her first transformations Janet had neglected to take care of her tail and it had ripped the leotard off her body as it grew longer, larger and thicker. Janet didn't necessarily need to wear clothes in her altered form - her scales not only covered the most intimate private parts of her body but were also fireproof and resistant to most types of conventional ammunition. But she still felt a little more comfortable having at least something to wear when she fought crime in public. Janet wasn't just some dumb wild animal or a thuggish brute!
Janet winced as her feet stretched, growing wider at the base and narrow at the heel. This was probably the worst part of the transformation. But it was also one of her favorite features of her persona. She playfully wiggled her large stubby toes, now the size of large sausages. An equally large, thick, sharp claw extended from each toe, clicking on the concrete below her feet as she constantly adjusted her stance while her feet continued to stretch and grow longer. Her reptilian feet required her to balance her massive weight on the balls of her feet and it always took her a little while to adjust, even with the help of her tail as a counterweight. Her toes had already merged into three digits with a small dew claw near the heel. Janet had given up hope of wearing any kind of shoes with her costume long ago. Even if she could have found something that would accommodate her odd feet without looking silly, they were unnecessary. The hard leathery pads underneath her feet were tougher than any protection a shoe could provide.
Janet's nose tingled and she sneezed as she saw some blonde hair drift past her face. She reached up and felt her pretty blonde hair falling out in clumps. She regretted the loss of her beautiful hair (her final form was devoid of any body hair) but the trail of spikes that ran across her head like a Mohawk was a pretty cool replacement. She could feel the spikes pushing out of her skin, continuing down her back to the tip of her tail. Larger, longer ones worked their way free at her elbow joint, as the bones in her forearms extended into large spikes.
The tingling in her face grew worse. Janet knew the transformation process was nearing its inevitable end. Her ears had already receded, leaving behind two small holes on her smooth head. Now it was time for her nose to change, getting broader and flatter as it pressed against her extending jaw. She opened and closed her mouth as her teeth elongated into thin, sharp needles. She blinked her eyes repeatedly, her vision getting blurry as the iris of her eyes began to shift into a thin vertical slit. She closed her eyes and ran her lengthening tongue across her aching gums. Her jaw finished strecthing into a snout with a loud crack.
Janet roared, feeling a mixture of relief and excitement.
It was over. Her transformation was complete.
Janet opened her eyes, now seeing the world in a different way. Her vision was more acute, with a wider field of vision. It was always a little odd seeing wavelengths in the UV range. She could taste the smell of her enemies as she flicked her tongue in the air.
She pounded one clawed leathery fist into another, eagerly anticipating the battle ahead.
"Let's do this, " said Janet, more growl than human words, as she ran out of the alley and confronted her enemy.