Lydia would be concerned about Stiles' mental state as a kid. She might try to engage him in activities that would stimulate his mind and keep him from getting too bored or scared. Scott would be constantly by his side, like a big brother. He'd try to include Stiles in their pack activities in a way that was appropriate for a child. Derek, on the other hand, would be more guarded. He'd be worried about the potential danger that could come to Stiles in this vulnerable state and would be on high alert to protect him from any threats, whether they're from the supernatural world or just regular people in town.
Scott would probably be very protective. He'd feel responsible for taking care of Stiles and making sure he doesn't get into too much trouble. Lydia might be initially shocked but then use her intelligence to try and figure out how to reverse the situation. And Derek, well, he'd probably be a bit annoyed at first but would also end up being one of Stiles' protectors.
His father would be extremely worried. He's used to Stiles being a teenager, and now he has to deal with a much younger version. He'd likely be calling in every favor he has to try and find a solution. The other members of the pack would have different reactions too. Some might find it funny at first, but then realize the seriousness of the situation. They'd all have to adjust their relationships with Stiles, like how they communicate with him. For example, they can't use the same complex language they used with the older Stiles.
In some fanfictions, a possible plot could be that Stiles, as a kid, has a different perspective on the supernatural world around him. He might not be as afraid as he was when he was older. For example, he could befriend a supernatural creature that the older Stiles would have been more cautious about. This new friendship could lead to new alliances for the pack. Also, his family's reaction to his sudden transformation could be explored. His dad might be really confused and worried, while his friends are trying to keep it a secret from the wrong people in town.
There might be a jealous friend or acquaintance who feels that Stiles, as a girl, is getting too much attention. This person could then start spreading rumors or causing trouble for Stiles in an attempt to bring her down.
One possible plot could be Stiles' struggle to adapt to his new female body. He might have to deal with different social expectations and how his friends react to his new appearance. Another plot could involve Stiles trying to find a way to turn back into his male self while facing various challenges along the way.
His friends would be devastated. Scott, for example, might go into a state of extreme anger and blame himself for not being able to protect Stiles. Lydia could be inconsolable, using her banshee powers to try and find some connection to Stiles in the afterlife.
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.
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.
His friends would be really shocked at first. Uraraka might be the first to try and comfort him, seeing as she has a kind heart. Bakugo, on the other hand, would probably be both confused and a bit angry at the situation. All - Might would likely feel a sense of responsibility to protect Deku even more than before. The teachers at UA would probably start researching how to reverse the transformation immediately.
Well, often in these fanfictions, Stiles becomes more confident. His physical appearance might also change, like he could start dressing better or have a new haircut that gives him a 'hot' look. For example, he might start wearing more stylish clothes that show off his personality.
Stiles might be initially shocked. He would probably feel betrayed since he thought of the pack as his family. He could go into a state of denial at first, not believing that they would actually kick him out.