At school

One day in the middle of a particularly boring math class Becky is struck by a sudden wave of nausea. Not wanting to make a fuss she tries to ignore it but the feeling grows until she is can't fight it off anymore.

"Sorry... I... need to go to the bathroom." She announces interrupting Mr Trent's explanation of trigonometry "Feel sick..."

Without waiting for a response she rushes out the door and into the hall. Swallowing hard to keep her lunch down she staggers to the bathroom. Stomach cramping she grabs onto a sink for support. Looking in the in the mirror she sees her face covered with a sheen of sweat and her skin has taken on a greenish pallor.

"Oh, shit" she groans "I'm really sick... need help."

She reaches into her purse for her phone but before she can dial it slips from her clammy hand to fall to the floor with a clatter. The muscles in her arm spasm and then the whole limb is abruptly sucked into her shoulder, vanishing without a trace. She gapes at the impossible sight of her suddenly empty sleeve flapping from her shoulder. She is too stunned to even be afraid until her other arm follows suit. Only then does she think to seek help but as she turns toward the door both her legs shrink away to nothing. Suddenly legless she falls forward landing hard enough to knock the wind out of her. By the time she catches her breath what remains of her body has already begun to shrink. Her backside tapers into a stubby tail. Her breasts merging into a barrel-shaped body. Her head and neck blending into her narrowing shoulder. She tries to scream but her mouth has become a lipless maw and she only manages an incoherent hiss. Everything goes dark as her clothes collapse in a pile around her still shrinking body.

What emerges from the pile a few minutes later bears no resemblance to Becky or any other human. She has become a grey/green slug covered in slime and just a few inches long.

"Ew ew ew," she thinks to herself "look at me, I'm fucking disgusting. What the fuck happened to me?"

As if answering her question strange new memories flood into her mind telling her all about her alien ancestry and the strange powers that come with it.

"Oh okay," she thinks frozen in shock by the sudden revelation "that makes sense, I'm an alien and I have superpowers?"

She isn't quite sure what to do with this information, fight crime, world domination? Neither choice seems particularly appealing, Maybe she should just try turning back into a girl?