He might start to question some of the norms in his own wizarding world. If he reads about how the characters in Supernatural deal with curses and dark forces without the use of spells like in his world, he could start to wonder if there are better ways in his own society. It could make him more critical of some of the traditional ways in Hogwarts and the wizarding community at large.
His view could become more open - minded. He'd realize there are other ways to approach the supernatural world. For example, the way the hunters in Supernatural use weapons instead of wands might make him think about alternative forms of magic defense.
Their view might expand. They'd see different takes on the wizarding world that they hadn't considered before.
His view of magic could expand. Anime often has very different interpretations of magic and superpowers. He might start to think more broadly about what magic can do and how it can be used.
Their view could become more confused. Fanfiction can present all sorts of alternate universes and character developments. The Death Eaters, used to a very specific view of the wizarding world under Voldemort, would find it hard to accept different versions. They might see the wizarding world in fanfiction as a chaotic and wrong place, which would make them double down on their own views to feel more secure.
After reading the fanfiction, Percy could have a more in - depth understanding of the wizarding world. He might start to think about how the social structure in the wizarding world compares to that in his demigod world. He might also be more curious about the history and lore of the wizarding world, and how it developed compared to his own world of Greek gods and monsters. He could even start to imagine what it would be like to be a wizard, with all the unique spells and magical items, and how that would change his approach to dealing with his own problems.
In fanfiction, Harry Potter can change the Wizarding World in many ways. For example, he might introduce new spells or magical concepts that were not in the original series. He could also have different relationships with other characters, which in turn would affect the social dynamics of the Wizarding World.
His view of magic might expand. In his world, magic is mainly about spells and potions. But after reading HTTYD fanfiction, he would see that magic can also be about the bond between humans and creatures like dragons. This could make him think more about the potential of magic in his own world beyond just what he has been taught at Hogwarts.
They may gain a deeper understanding of how the outside world perceives their world. Fanfiction often reflects the hopes, dreams, and fears that fans have about the wizarding world. So, by reading it, the Potter family can get a sense of what others find interesting or concerning about their world. For instance, if a lot of fanfiction focuses on the social inequalities in the wizarding world, it might make them more aware of these issues and perhaps even inspire them to do something about it.
His view could become more broad. He'd see that magic can be manifested in ways other than what he's used to. For example, the zanpakuto in Bleach have unique powers that are different from any wand magic he knows.
Well, Harry's immortality would bring about a great change in the wizarding world. Since he can't die, he could be a source of hope for a very long time. He might inspire new generations of wizards to be braver. Also, the way magic is used and perceived could change. For instance, people might study his immortality to find ways to extend life in general. And his influence on the fight against dark forces would be continuous, not just a one - time deal like in the original story.
If Harry invented spells like 'Teleporto Instanto', which allows for instant teleportation anywhere in the wizarding world, it would completely revolutionize travel. People could go from Hogwarts to Diagon Alley in a blink. It would also change the way battles are fought as wizards could quickly escape or surprise their enemies.