Hermione could be one of the characters. Given her know - it - all nature, she might think Harry needs her constant guidance and end up treating him like a baby. She might constantly correct him and not let him learn from his own mistakes. Ron could also be one of them. Maybe out of his over - protectiveness for his friend, he might not let Harry do certain things he deems dangerous, like facing a small magical creature on his own.
One common situation could be that the other characters in the fanfiction might constantly over - protect Harry. For example, they don't let him take any risks or do things on his own, like going to the Forbidden Forest even for a small exploration. Another situation could be that they talk to him in a very patronizing tone, as if he doesn't understand anything. Maybe they try to feed him or dress him as if he were incapable of doing these basic things himself.
He could get angry. Harry has a strong will, and being treated like a baby would likely bruise his ego. He might lash out at the people doing it, shouting things like 'I'm not a baby! I've faced Voldemort!' to make them realize he's more capable than they think.
Another possibility is that they dress him in baby - like clothes. Picture Harry being forced to wear frilly or overly childish robes that make him look like a toddler. This could be part of the way the other characters infantilize him, perhaps as a form of protection in their minds, but it's really demeaning to Harry.
The popularity of 'Harry Potter treated like a baby fanfiction' might also stem from the fact that it can explore deeper emotional relationships. When Harry is a baby, the other characters have to show different levels of care and love. This can be used to develop the relationships between characters in new ways. For instance, Snape might have a different attitude towards baby Harry if he has to protect him, which can be an interesting exploration of his complex character. Also, fans might enjoy seeing a more innocent and helpless version of Harry, which contrasts with his usually brave and heroic self in the original series.
Typically, there's the kidnapper. This character is often portrayed as having some sort of psychological issue or a very warped sense of control. Then there's the victim, who is usually an adult or older teen that is forced into this baby - like treatment. There might also be secondary characters like the victim's friends or family who are searching for them, adding an element of the outside world trying to break into this strange situation.
One example could be a story where Harry is magically regressed to a baby state and the Dursleys have to take care of him in a more affectionate way than in the original books. Another might be a fanfic where the wizarding world decides to protect baby - like Harry by hiding him in a nursery filled with magical protections.
The baby could be a very energetic and curious little one, always getting into things around the house, much to the amusement and sometimes exasperation of Harry and Susan.
Obviously, Peter Parker himself is the main character. Since he's the one being treated like a baby.
Sometimes it can be due to misperception. If a child has long hair or delicate features, people might assume they are a girl and start treating them as such. This can lead to the child being treated like a girl baby even if their parents or caregivers don't initially intend it. And in some cases, it could be that the caregivers are just following traditional gender - based behaviors that they think are cute or endearing without really thinking about the long - term impact on the child's sense of self.
It could mean a fanfiction where a character is being treated as if they were a baby. Maybe in the story, they are coddled, protected, or infantilized in some way by other characters.