One possibility is that Percy turns into a falcon. He could then use his new form to spy on his enemies from above. With his sharp eyesight, he might discover hidden lairs or secret meetings. This would give him an advantage in the story's battles or quests.
Maybe Percy turns into a dolphin. As a dolphin, he could swim freely in the ocean, exploring underwater kingdoms that were previously inaccessible. He might encounter friendly sea creatures who help him on his journey or face off against dangerous sea monsters in the deep.
Perhaps Percy turns into a falcon. In this form, he could soar through the skies and spy on his enemies from above. He might use his falcon eyes to find a secret lair of a villain or to track the movements of the Titans. It would also give him a different perspective on the world around him, seeing things from a bird's - eye view.
One possible plot is that Percy, now a girl, has to deal with the expectations society has for girls in that fanfic's setting. She could struggle with things like how she's supposed to dress or act. And there could be a whole new dynamic with her enemies too. They might underestimate her because she's a girl, but then she proves them wrong with her skills and courage, just like she did when she was male.
One possible plot twist could be Percy's struggle to adapt to the new gender. For example, she might face challenges in how society now treats her. Maybe she was used to certain privileges as a boy that are now different. Another twist could be in her relationships. Her friends might react in various ways, some being very accepting while others are confused or even distant at first. And she could also discover new aspects of herself, like different interests or ways of expressing emotions that were suppressed before.
One possible plot could be that Percy, as a child, has to navigate his newfound smallness while still having the memories of his older self. He might struggle to convince his friends that he is actually Percy, and they initially think it's some sort of trick. Then, he could use his knowledge from his older self to help them in a new and unexpected way, like solving a mystery that the younger versions of them couldn't figure out on their own.
Well, one possible plot could be Percy struggling with his new identity. He might have to deal with how his friends react. For example, Annabeth could be initially shocked but then help him adjust. Also, Aphrodite might have done it as a test of some sort, like to see if Percy can understand the female perspective better, which could lead to some interesting adventures where Percy, as a girl, has to face challenges in a different way than before.
The fanfiction could start with Artemis getting angry with Percy for some reason, like he disrupted one of her hunts. So she uses her powers to turn him into a jackalope. As a jackalope, Percy is small and vulnerable, but he also has some unique skills. He can jump really high, which he uses to escape from predators. His friends are shocked when they see him, but they quickly decide to help him. They go on a journey to find Artemis and ask her to turn him back. On the journey, Percy has to deal with being hunted by other creatures who see him as an easy target, and he also has to learn to control his new body.
Well, one possible plot could be that Hestia has some grand plan. Maybe she turns Percy into a girl to teach him a lesson about seeing things from a different perspective. For example, he might face different challenges as a girl in the world of the story, like how people treat female characters differently in that fictional universe.
One possible plot could be Percy waking up as a girl and having to deal with the new physical and social aspects in Camp Half - Blood. Maybe the other campers are initially confused, but then they see that Percy (now a girl) still has the same heroic spirit and skills. She could go on a quest where her new female form gives her a different perspective on things, like how she interacts with female monsters or how she is treated by male gods differently.
Perhaps Artemis is testing Percy in some way. By turning him into a girl, she wants to see if he can still be as brave and resourceful. The plot could involve Percy learning about the female experience among the demigods. He could discover new aspects of friendship with female characters who now see him as one of their own. And he has to figure out how to reverse the transformation while also dealing with the current challenges.
One possibility could be that Percy, as a demon, struggles with his new identity. He might have to deal with new powers that are difficult to control. For example, he could accidentally harm his friends. He may also face discrimination from those who fear demons, even though he's still the same person deep down.