If Harry meets someone else first, it could completely change his character development. For instance, if he meets a more cynical wizard at the start, he might become more guarded or less trusting compared to the Harry we know who met Ron and Hermione first.
The plot would likely be very different. Instead of going straight to Hogwarts with Ron and Hermione, he could be diverted to other places. Say he meets a wizard who is on a mission to find a lost magical artifact, and Harry gets dragged into that adventure. This would mean missing out on some of the early Hogwarts experiences and relationships that were important in the original story.
The relationships in the story would be altered. If Harry meets a new person first, that person could become his closest confidant instead of Ron or Hermione. This would lead to a different dynamic within the trio, or even form a new group entirely. The new person might have different values or goals that influence Harry's actions and decisions throughout the series.
It could be a random wizard or witch from another school. Maybe a student from Beauxbatons or Durmstrang who crosses paths with Harry before he meets Ron or Hermione. This could lead to a whole new set of adventures and friendships that change the course of the story as we know it.
Maybe he meets an exchange student from a different magical school. For example, a student from Beauxbatons or Durmstrang. They could share their different magical cultures and knowledge with Harry, and together they could face some challenges that require a combination of their unique skills.
They could go on an adventure to find a lost magical artifact. The two of them would have to face various obstacles, like dark creatures and complex spells set to protect the artifact.
It could add a new dimension to Harry's relationships. Instead of just having his main friendships with Ron and Hermione, having Daphne in the picture early on might change the way he views Slytherins. This could lead to a more inclusive Hogwarts, where the house rivalries are less intense.
One popular 'Harry Potter is someone else fanfiction' could be those that reimagine Harry as a different type of wizard, like a wizard from a different magical culture. For example, there might be fanfics where he is more in tune with the ancient magic of the druids.
It's appealing because it allows fans to explore different possibilities. We get to see Harry in a new light, which can be exciting.
It could be a whole new adventure or a twist in the afterlife. Maybe it's a reunion with a long-lost friend or an encounter with a mysterious figure.
In many of these fanfictions, Sirius Black could be an alternative caregiver. He was Harry's godfather, after all. He had a strong connection to Harry's father and would have been a natural choice to raise Harry if not for his imprisonment. He was brave and had a strong sense of family loyalty.
In this kind of fanfiction, the prophecy about Harry might be interpreted differently. His metamorphmagus ability could be seen as an added factor in his fight against Voldemort. He could use it to deceive Voldemort and his Death Eaters, making it harder for them to target him. Also, the way he interacts with the wizarding community would change. People might be more in awe or more suspicious of him because of his unique ability, which would impact his social standing and the way he is perceived in the overall story.
In such a fanfiction, perhaps Harry Potter could use magic to communicate with the aliens. For example, he might use a spell to translate their strange languages.