Obviously, Harry Potter himself. And there could be characters like Hermione and Ron who might either go with him or be involved in some way from afar. There may also be original characters created for Alfe, such as an Alfe wizard who becomes Harry's guide.
Another potential character could be a wise old wizard in Alfe who has knowledge about a great power that Harry is somehow connected to. Also, there might be a group of young Alfe witches and wizards who look up to Harry and want to learn from him. They could be like a new group of friends for Harry, each with their own unique abilities and personalities.
There could be a villain in Alfe. This villain might be jealous of Harry's fame and power from his own world. He or she could try to undermine Harry's efforts to help Alfe or even try to use Harry for their own gain. This would create a lot of conflict and drama in the fanfiction.
Well, perhaps Harry could discover a whole new magical world in Alfe. He might meet new magical creatures and learn different kinds of magic that are unique to that place.
Obviously, Harry Potter himself. Then there could be Hermione and Ron, who might visit him at Harvard or communicate with him via magic. There could also be new characters like his Harvard roommate, who could be a normal Muggle but start to suspect that Harry is not an ordinary guy. And maybe some professors at Harvard who take an interest in Harry's different way of thinking.
In this 'harry potter goes to the sixth world fanfiction', we would expect Harry Potter. Besides him, there might be new wizards or witches native to the sixth world. They could have their own unique powers and personalities. Maybe there are also some half - magical beings that Harry has never encountered before. These new characters would add more complexity and freshness to the story.
He could meet an Egyptian wizard who is an expert in ancient magic. This wizard could teach Harry a great deal about the history of magic in Egypt.
Obviously, Harry Potter himself. There could also be some Beautox - natives, like a wizard or witch who is an expert in Beautox magic. Maybe Hermione would somehow find a way to follow Harry and she'd be there too, trying to figure out the new magic system.
Obviously, Harry would be one of the main characters. There could also be local Harlem residents like a street - smart kid who shows Harry around. A jazz singer could be another character, perhaps someone with a mysterious past that Harry gets involved with.
Hermione would be a likely companion. She loves learning and exploring, so she'd be eager to go on a traveling adventure with Harry. Ron might also tag along, especially if there's a chance of food and adventure. Neville could be another option. He has grown a lot in courage and his knowledge of plants could come in handy in different magical environments. Luna Lovegood would be a very interesting companion too. Her unique perspective on magic and the world would add a lot of fun and mystery to the journey.
Potential new characters might include a young American wizard called Tommy. He's a bit of a troublemaker but has a good heart. There could also be an old and wise American wizard professor, Professor Anderson, who teaches Harry about the history of American magic. And then there's a female wizard, Sophia, who is very interested in the British magic system and befriends Harry to learn more.
Obviously, Buffy would be a major character he'd interact with. They could start off as wary of each other but then grow to respect one another's fighting skills. Giles too, as he has a wealth of knowledge about the supernatural, and he and Harry could have some interesting discussions about different types of magic.
Obviously, Harry Potter himself. There would also likely be Viktor Krum, who is from Durmstrang. Krum could be either a friend or a rival to Harry. Igor Karkaroff, the headmaster of Durmstrang, would be another important character. And there could be new students created for the fanfic, like a Durmstrang student who becomes Harry's guide in the new school.