In this fanfiction, it could start with Ron stumbling upon a strange artifact in a forbidden part of Hogwarts. Touching it turns him into a fiend. His new form makes him a target of the wizarding world's authorities who think he's a dangerous creature. Meanwhile, his friends are trying to prove his innocence and find a way to change him back. They might have to search for a rare magical ingredient or learn a powerful spell to reverse the transformation.
Well, perhaps it could be about Ron being cursed by a dark wizard. He then starts to show fiend - like behavior, like craving for chaos and destruction. His friends initially don't recognize what's wrong with him and try to figure out how to reverse the spell.
The main antagonist could be a jealous classmate. This classmate is envious of Ron's friendship with Harry and Hermione. So, they find a way to use dark magic to turn Ron into a fiend, hoping to drive a wedge between them. However, as the story progresses, they realize the consequences of their actions are far more serious than they thought.
One possible plot could be that Ron gets turned undead in a magical accident. Maybe he was exploring a dark and forbidden part of Hogwarts and stumbled upon an ancient curse. As an undead, he has to deal with his new state while his friends, like Harry and Hermione, struggle to find a way to reverse it. He might have new powers and cravings that are both a mystery and a danger.
It could be a dark wizard who has a long - standing vendetta against Ron's family. This wizard might see turning Ron undead as a way to get revenge on the Weasleys. He could be lurking in the shadows, trying to make Ron's undead state even worse by casting more dark spells on him.
Maybe Ron accidentally ruins Hermione's important experiment in the wizarding lab. In the fanfiction, Hermione could get revenge by getting all their mutual friends to side with her in an argument. She could present all the facts about how Ron's carelessness has cost her time and effort, making Ron feel isolated and guilty.
Well, one possible plot could be that Ron discovers his superpowers accidentally. Maybe he gets exposed to some strange radiation or a magical artifact. Then he has to learn to control these powers while still dealing with his normal life, like school and his friends. Kim might be initially skeptical but then becomes his ally in using the powers for good.
Perhaps it's a prank gone wrong. A group of Gryffindors, thinking they could teach Draco a lesson, cast a spell on him that they thought would just embarrass him. But instead, it turns him into a baby. Now, Hermione, being the brilliant witch she is, feels responsible for finding a cure. She starts researching in the library, while Ron is left to keep an eye on baby Draco. Ron has no idea how to take care of a baby, and there are lots of comical moments as he tries to feed Draco and keep him from crying.
In a 'Seto gets turned into a child fanfiction', the plot might revolve around Seto's own struggle to adapt to his new form. He's used to being in control and powerful, but as a child, he has limited abilities. He could try to communicate with others about what happened to him, but with his child - like speech and behavior, it becomes a challenge. His friends might have to protect him from those who would take advantage of his vulnerable state.
Well, one possible plot could be that Ichigo is turned into a neko by a powerful magical being as a form of punishment. He then has to learn to live with his new feline features while still trying to protect his friends and fight against the Hollows. Maybe he struggles with his new instincts like chasing after small moving objects at first, which could add some comical elements to the story.
One possible plot could be that Ash wakes up one day as a girl and has to deal with all the changes in his daily Pokémon adventures. For example, he might have to adapt to new clothing styles and different social interactions. His Pokémon might also react in various ways to his new form.
Maybe it starts with a strange magical experiment gone wrong in Hogwarts. Harry is curious and gets too close, and suddenly he's a baby. The story could then focus on how the teachers, especially Dumbledore, deal with this situation. They might try to figure out if this is a new form of dark magic they haven't seen before. And Harry, as a baby, would have no memory of who he is, so it could also be about his friends trying to make him remember bits of his past life.