One possibility could be that Percy, as a new god, would have to deal with the complex politics of Olympus. He's always been an outsider, and now he'd be thrust into a world of power plays and ancient rivalries. Maybe he'd try to change some of the archaic rules that the gods have held onto for centuries.
One idea could be that Percy turns into a dragon to fight a powerful sea monster. Since he has his connection to water, as a dragon he could breathe a sort of water - based fire or ice that freezes the water around the monster, trapping it.
One idea could be that Percy discovers a demigod child who has been abandoned in the mortal world. He decides to adopt the child to protect them from monsters and to give them a proper home at Camp Half - Blood. He then has to teach the child about their demigod heritage and how to use their powers.
One great 'child percy jackson fanfiction' is 'Percy Jackson and the Quest for the Lost Artifact'. It has an exciting plot where Percy and his friends embark on a new adventure outside of the main series' storylines. The characters are well - written and stay true to their original personalities.
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.
In a 'Percy Jackson turns evil' fanfiction, he might use his powers against his former friends. For example, his control over water could be used to flood Camp Half - Blood. His knowledge of the demigod world would also be a weapon in his hands to outwit and defeat those who oppose him.
Well, in the fanfiction, if Percy turns into a baby, he would probably lose all his skills and knowledge at first. But he might still have some instinctual connection to water. Maybe his friends like Annabeth would have to take care of him. She'd be really protective and try to find a way to turn him back.
In the 'Percy Jackson turns into a cat' fanfiction, he could end up in some really interesting situations. For example, he might be chased by some of the magical creatures at Camp Half - Blood that don't recognize him as Percy. His senses would be heightened as a cat, so he could detect things like danger or hidden treasures more easily. Also, it would be hilarious to see how Annabeth reacts when she first sees Percy as a cat. She might be confused at first but then try to figure out how to turn him back.
The antagonist could be a group of bullies in the story. They pick on Percy because he is now a child and seems weaker. They don't know he is actually Percy with all his heroic qualities. They constantly harass him, steal his things, and try to make his life miserable. This forces Percy and his friends to come up with strategies to deal with these bullies, which could include using Percy's unique skills even in his child form, like his ability to talk to sea creatures to get help when the bullies try to corner them near the water.
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.