I think Neville could be a key character. He was often overlooked in his Muggle school days, but now as a capable wizard, he could show up at the reunion and surprise everyone. Ginny might also be there. She's bold and confident, and she could handle any strange situations that might arise at the reunion. And Luna could add her unique, dreamy perspective to the whole event.
Hermione could be a main character. Since she was a Muggle - born witch, her Muggle schoolmates might be very curious about her new life. Harry could also be involved as he had some experience in the Muggle world. Maybe even Ron, as he's always curious about Muggle things. Their presence would bring an interesting dynamic as they try to balance their wizarding selves with the Muggle environment of the reunion.
Well, there could be a lot of drama. Maybe some of the Muggle schoolmates were jealous of the wizarding kids back then. At the reunion, they try to cause trouble. Or it could be a really heartwarming story where the Muggle friends finally understand why their friends were a bit different. They might see how the magic has been used for good in the wizarding world, like helping the injured or protecting the innocent.
She might meet her old teachers. They would be surprised to see how much she's grown and changed. And of course, her former classmates. There could be the popular girl from school who is now a bit jealous of Hermione's confidence. Or the nerdy boy who has now become a successful scientist and they can have an interesting exchange about different kinds of knowledge, magical and Muggle.
Luna Lovegood could be a main character too. She always had a unique perspective on things at Hogwarts. At the reunion, she might share some of her strange but fascinating adventures since leaving school, and her presence would surely add a touch of whimsy to the gathering.
Well, it could be a group of ordinary Muggles who rise to be leaders in the Muggle Army. Maybe there's a tech - savvy Muggle named Tom who uses his knowledge of electronics to find ways to detect magic. He could be one of the main characters.
In this kind of fanfiction, the main ones would be the Potter family. But it would also include Sirius Black if the story allows for his presence in some way, like a magical resurrection. Remus Lupin's family might be there too, if Tonks and their son Teddy were to be part of the reunion. And of course, the whole Weasley clan, from the eldest siblings to the youngest grandchildren, all gathering together to celebrate family.
Obviously, Harry Potter himself would probably be there. Hermione Granger would also likely make an appearance. Ron Weasley would surely come along with his typical sense of humor. Neville Longbottom might show up, now a much more confident wizard. Luna Lovegood could be there too, with her unique perspective on things. And perhaps some of their less - known classmates from primary school would also be present, like Dean Thomas or Seamus Finnigan.
Hermione would surely be one. She's smart and would be great at helping with the academic side of building a school, like creating the curriculum.
Often, you'll see Harry Potter himself. He might be involved in helping a muggle adjust to their new lordship in the wizarding world.
Hermione could be a main character. She might be initially skeptical about Harry singing muggle music, but then she gets interested in the cultural aspect of it and starts researching the history of the muggle music Harry likes.
Harry himself is obviously very popular. He's the main character in the original series, so in the 'Harry Potter Goes Muggle' fanfiction, readers are interested in seeing how he copes in the Muggle world. Hermione is also popular. Her intelligence and quick - wittedness make for interesting scenarios in the Muggle world, like helping Harry with Muggle studies.