There could also be some original characters created for the fanfiction. For example, a new student who befriends Harry when he is dressed as a girl and has no idea that it's actually Harry Potter. This new character could add a whole new dynamic to the story.
In addition to the main ones, characters like Shampoo and Ukyo might play important roles. Shampoo, who has her own feelings for Ranma, may have a different approach to a female - Ranma. Ukyo too, might have a new dynamic with Ranma in this situation. And of course, there could be other minor characters from the original series that get involved in the fanfiction, depending on the author's creativity.
Well, Naruto is the main one. But also, Kakashi could be involved. He might be a bit amused at first but then help Naruto figure out how to use his new body to his advantage in combat. And then there's Hinata. She could have an interesting reaction, perhaps being more shy around Naruto as a girl, or she could be more empathetic as she also has her own insecurities.
Hermione Granger is also a common character. Given her love for knowledge and her skills in magic, she would likely be researching the best spells and magical theories to make the terraforming successful. She might be the one to find ancient spells that are crucial for the process.
In many expelled Harry Potter fanfictions, the Weasley family as a whole gets involved. Molly Weasley would be worried sick about Harry and would be cooking up plans to get him back. Fred and George might use their prank - making skills to expose the truth behind the expulsion. Ginny, being Harry's love interest in the original series, would be actively involved in trying to clear his name. And don't forget about the Hogwarts professors. McGonagall would probably be torn between following the rules and believing in Harry.
Harry Potter himself is often a central character. He might be shopping for new school supplies at Flourish and Blotts or looking for a new broomstick at Quality Quidditch Supplies. His friends, like Hermione and Ron, usually accompany him. Hermione might be more interested in books and rare magical artifacts, while Ron would be eyeing the latest Quidditch gear.
Mrs. Weasley is a very likely character. She's an expert at cooking and baking in the normal wizarding world, so in fanfiction about magical bakes, she could be teaching the younger characters how to make special bakes. Hagrid might also be involved. He could bring in some really strange ingredients from the Forbidden Forest, like giant acorns, to be used in the bakes.
Hermione Granger is often involved. In some fanfictions, she discovers hidden conspiracies within the Hogwarts library. For example, she might find a book that reveals a plot by some of the older pure - blood families to keep certain magical knowledge from half - bloods and Muggle - borns.
Obviously, Harry Potter himself is the central character. His friends like Ron Weasley and Hermione Granger are also often involved. They might try to visit him while he's grounded or come up with plans to get him out of being grounded. Dumbledore could also play a role, either as the one who enforces the grounding in some cases or as the one who might offer some wisdom to Harry during his time of confinement.
Obviously, the wonder girls themselves are the main characters involved. They could be from different teams or generations of wonder girls.
Harry Potter himself is often a common character. He might be the one who accidentally stumbles upon the hypnosis magic and ends up with a harem. Hermione Granger is also frequently included. Her intelligence could be used in different ways in the story, like helping to understand the hypnosis magic better or being an important part of the harem dynamic. Ginny Weasley is another character that can be part of the harem. She has her own strong - willed personality that can add interesting twists to the story.