If Harry is adopted by the founders in fanfiction, his whole life would take a different turn. Firstly, his living situation would be different. He'd be living in an era closer to the origins of Hogwarts, which means different architecture, different social norms among wizards. The founders would shape his magical education. Gryffindor might encourage him to be even braver, and Ravenclaw could help him develop his intellectual side more. His relationships would also be different. He might not have the same friends as in the original story, and his enemies might be different too. All in all, it would be a very different Harry Potter story.
In such a fanfiction, Harry might gain access to ancient magic knowledge. The founders, being from a different era, could teach him things not available in his own time. He may also experience a very different Hogwarts, perhaps one more in line with the founders' original vision.
If Harry was adopted by the founders in fanfiction, it would completely change the story's dynamic. He'd likely be exposed to a purer form of magic. Maybe he'd be taught in a Hogwarts that was still in its infancy, and be part of building the school's traditions. His relationships with other characters would be different too. Instead of having Ron and Hermione as his closest friends from the start, he could befriend students from different eras who were also learning under the founders.
Well, it would be a very interesting story. Harry would be exposed to a much more primitive form of magic. The founders could give him access to magic that has been lost over time. He might grow up with a stronger connection to the roots of Hogwarts. Also, there could be conflicts among the founders on how to raise Harry. Godric might want him to be a fearless warrior, while Salazar could have other ideas about his future. This would create a lot of drama and tension in the story.
In the 'Harry adopted by the Malfoys' fanfiction, one possibility is that Harry would receive a very different kind of magical education. The Malfoys might try to mold him into a Slytherin - like wizard, but Harry's own Gryffindor - like courage would constantly be at odds with that. Also, his relationship with Draco could be very complex, ranging from initial rivalry as they are brought up in the same household to a possible understanding and even friendship later on.
In such a fanfiction, Harry might be raised with a very different set of values. Voldemort could try to mold Harry into his own image, perhaps teaching him dark magic. But Harry might also secretly hold on to his own sense of good. For example, he could use the knowledge Voldemort gives him to ultimately turn against him.
If Harry was adopted by the Joker in fanfiction, it could lead to some really interesting character development. Harry might start to develop a warped sense of humor and a disregard for the law like the Joker. On the other hand, he could also be a source of conflict within the Joker's world. Maybe Harry would try to resist the Joker's influence and secretly work towards bringing him down. It would be a battle of wills between the two, with Harry having to use his wits to survive in the Joker's crazy world.
In such a fanfiction, Harry's life would be extremely different. Bellatrix is a Death Eater, so Harry might be indoctrinated into dark magic. However, his strong will from his original upbringing might resist this. He could be in a constant internal struggle between the light he was initially inclined towards and the dark teachings of Bellatrix.
In such a fanfiction scenario, Harry might have a very different upbringing. He could be exposed to a more academic and Muggle - centered environment. The Grangers, being dentists, might encourage him to pursue a more traditional Muggle career while still being aware of his wizarding heritage. He would probably grow up with a strong sense of discipline and study habits from them.
In the 'Harry adopted by the Winchesters' fanfiction, there are a lot of possibilities. Harry could bring his knowledge of potions and magical artifacts to the Winchesters. This could be useful in dealing with some of the more dangerous supernatural threats. The Winchesters, on the other hand, could teach Harry about survival in a more 'normal' but still dangerous world. Their skills in tracking, weapons handling, and understanding human nature could be invaluable to Harry. Also, the relationships between Harry and the individual Winchesters would be complex and evolving. There could be moments of conflict as they come from very different backgrounds, but also moments of great bonding as they face various challenges together.
His personality might become more traditional in some ways. Since the founders are from an earlier time, their values could rub off on him. He might be more reserved like some of the older wizards.
The fanfiction 'Harry Potter adopted by vampires' could be really interesting. Harry would be exposed to a very different culture. Vampires are often depicted as nocturnal, so Harry might have to adjust his sleep schedule. His magical abilities could interact in unexpected ways with vampire characteristics. He might also face discrimination or fear from both the wizarding world (who may not trust vampires) and the vampire world (who may not trust a wizard). It could be a story full of conflict, self - discovery, and new friendships as he tries to find his place in this strange new world.