Harry Potter would be the central figure as he is the protagonist in his own series. Ron could also be there, providing his usual comic relief and loyalty. As for Pokémon characters, it could be that a trainer from the Pokémon world somehow gets transported to Hogwarts. This trainer, along with their Pokémon, could become main characters. For instance, Ash Ketchum and his Pikachu could end up in the wizarding world. Harry, Ron, and Hermione would then interact with them, leading to all sorts of interesting situations. They could learn from each other's worlds, like the Pokémon trainer learning about magic and the Hogwarts students learning about Pokémon catching and training.
In addition to Harry, Neville could be a main character in this fanfiction. He has a connection to the magical creatures in the Harry Potter world already. And from the Pokémon side, a Pokémon like Charmander could be a main character. Imagine Neville befriending Charmander and trying to figure out how to take care of it in the Hogwarts environment. They could face challenges together, like dealing with other students who might be scared of the Pokémon or trying to hide it from the professors.
Obviously, Harry Potter would be one of the main characters. And maybe Hermione, since she's always interested in new and strange things. Also, a Pokémon like Pikachu could be a sort of main character in its own way, as it's the iconic Pokémon.
Obviously, Harry Potter himself would be a main character. He is the heart of any Hogwarts - related story. Also, Ron Weasley and Hermione Granger, as they are Harry's closest friends and would surely be part of his first Christmas at Hogwarts.
There could also be a trainer who is jealous of Harry's unique abilities, being reborn from the Harry Potter world. This trainer might try to undermine Harry at every turn, stealing his Pokemon or sabotaging his battles, much like Draco Malfoy was often in conflict with Harry in the original Harry Potter series.
It could be Neville Longbottom. Neville is often overlooked in the Harry Potter series. He could be the one to discover a neglected Pokemon, like a Bulbasaur that has lost its trainer. Neville, with his kind heart and new - found confidence, decides to take care of the Bulbasaur. He uses his skills in Herbology to help the Bulbasaur thrive, and they form a great team.
Well, it could be about Harry Potter somehow finding a Pokémon in the wizarding world. Maybe a Pokémon gets magically transported there, and Harry has to figure out what it is and how to deal with it.
Obviously, Harry Potter would be one of the main characters. And the first vampire would be a central figure too. There might also be characters like Hermione and Ron, who could be involved in the story in different ways. For example, Hermione might be researching about vampires to help Harry understand the situation better.
Neville Longbottom could be a main character. He has always had the potential for great things and in a world without Harry, he would be likely to step into the spotlight. He has the courage and the connection to Hogwarts that could make him a central figure in the fight against evil.
Hermione could also play a role. Given her intelligence and love for learning, she might take an interest in accounting to better manage the finances of the various causes she's involved in, like the Society for the Promotion of Elfish Welfare. So she could be a main character or at least a supporting one in this fanfiction.
Obviously, Harry Potter himself could be a main character. He could be the one who is initially reluctant to participate in a dance event but then discovers a new passion for it. Hermione could also be a main character as she might be the one researching the history and significance of different wizarding dances.
In addition to the main trio from the Harry Potter series, there could be some of the Hogwarts professors as main characters. For example, Professor Dumbledore might have some knowledge about the balverines that he imparts to Harry. And Hagrid, with his love for all kinds of strange creatures, could be involved in trying to tame or at least understand the balverines better.
Harry, Hermione and Ron could be the main characters, exploring the mysteries of the mansion. Or perhaps a new generation of wizards, like the children of the original trio. Neville Longbottom could also be a main character, using his knowledge of plants to uncover secrets in the mansion's garden.