One possibility is that Batman discovers the kid - Joker. At first, Batman might be extremely confused. But instead of treating him like an enemy, he decides to protect him. As a kid, the Joker could start to look up to Batman as a hero, and this could create a really strange and complex relationship between them. Batman could try to guide him towards a good path, while also being on guard in case the old, evil Joker resurfaces.
Well, he might lose all his evil cunning at first. Since he's a kid, he could start to see the world in a more innocent way. Maybe he'll make friends with people he used to terrorize, not realizing who they are. And he could be easily influenced by good-hearted characters, starting to develop a sense of right and wrong that's completely different from his adult, villainous self.
If Deadpool is turned into a kid in fanfiction, it would be a total shift in his character dynamic. His relationship with other characters would change drastically. For example, his friends might have to take on a more parental role. And his enemies might not take him as seriously at first, but he could still surprise them with his child - like cunning. Also, his origin story would be interesting to re - imagine from a kid's perspective, how he discovers his powers and all that.
Well, in such a fanfiction, Sonic might lose his usual speed and confidence at first. He'd probably be more naive and rely on his friends more. Maybe he'd have to learn basic things all over again, like how to properly control his powers in his new, smaller form.
The other villains in Gotham. The power dynamic changes when the Joker is a kid. They might see this as an opportunity to take over his territory or try to use the situation to their advantage. But they also might be worried that if the Joker turns back to normal, he'll come after them for taking advantage of his weakened state.
Well, he might lose all his skills and knowledge at first. For example, he probably wouldn't be able to handle his sword as well as before. He could be really confused about his new small body and the world around him that now seems so much bigger. His friends would have to take care of him like a real little kid, feeding him, dressing him, and making sure he doesn't get into too much trouble. Maybe he would also start to see things from a completely different perspective, like being more innocent and curious about simple things that he used to take for granted.
In the fanfiction, Kagome's enemies could underestimate her. They think that because she's a child, she's not a threat. But in reality, even as a child, Kagome still has her strong will and some of her powers. She could surprise them by using her wits and the little bit of spiritual power she has left to outsmart them. For instance, she could lead them into a trap that her friends set up.
He could start to notice things from a different perspective. As a girl, Bakugou might become more aware of the way others perceive her appearance. She might also start to develop different interests, like taking more interest in fashion or something that she previously didn't care about. This could lead to some really interesting character development, especially if she still tries to hold on to her tough - guy (or now tough - girl) attitude.
Well, he might start to see the world from a Pikachu's perspective. For example, he would experience the small size and how everything looks so huge. He could also find it difficult to communicate with his human friends in the normal way since he is now a Pikachu. Maybe he would have to rely on Pikachu's ways of expressing emotions like using electrical signals.
Well, she might struggle with her newfound vampire nature. Maybe she has a hard time controlling her thirst for blood and accidentally attacks someone she cares about.
Well, it could also create some conflict. If the bone weave is an experimental or rare technology, there might be those who oppose Joker getting it. This could lead to internal strife within the crew or between different factions in the Mass Effect universe. It might also attract unwanted attention from enemies who want to study or steal the bone weave technology from him.
It might be due to some scientific experiment gone haywire. In a fanfiction world where science and ninja techniques are combined, an experiment that was supposed to enhance Sasuke's abilities could have had the unexpected side - effect of changing his gender. This could lead to all sorts of interesting plot developments, like how he copes with his new physical form and how his relationships with other characters change.