Tinkerbell could be a new kind of magical creature in the wizarding world. She might be discovered by Hagrid in the Forbidden Forest. Since she's so small, at first the wizards might mistake her for a really tiny pixie. But then they'd realize she has different powers, like being able to create light and fix things with her fairy dust.
In a more complex scenario, Tinkerbell could be from a parallel magical dimension that starts to merge with the Harry Potter universe. This causes all kinds of chaos as the rules of magic from both worlds start to mix. Tinkerbell has to work with Harry Potter and the other wizards to find a way to separate the dimensions again before it's too late. She uses her knowledge of her own world's magic, which is very different from wizard magic, to help solve the problem.
Supergirl could be a foreign exchange student of sorts in the Harry Potter universe. She could be there to study magic while also sharing her own Kryptonian knowledge. Her superpowers would make her stand out, but she would also have to learn the rules of the wizarding world, like not using her powers when it's against the wizarding code.
Imagine an Aztec warrior as a protector of a powerful magical artifact that has some connection to the Harry Potter world. Voldemort is after this artifact, and the Aztec warrior teams up with Harry and his friends to keep it safe. Along the way, they learn from each other's cultures and magics.
He could fit in as a new kind of hero. His magic would be something unique compared to the existing powers in the Marvel world. He might join the Avengers and use his spells during battles. For example, he could stun enemies with a simple 'Stupefy' spell or create a large magical explosion with a more powerful incantation.
In a more complex fanfiction, a Sith Assassin could be the result of a long - lost experiment by a powerful but mad wizard who tried to combine the dark arts of the wizarding world with some unknown, extra - dimensional power that led to the creation of this Sith - like being. This being then has a connection to both the Sith ways and the magic of the Harry Potter universe. It could be on a quest to either gain more power or to find a way to belong in this strange world that it has been thrust into.
A Gun Mage could be a product of a long - lost magical branch. They could be discovered by Harry Potter and his friends during an adventure outside of Hogwarts. Maybe they were hidden away for centuries because their magic was considered too dangerous. Once they enter the main story, their gun - based magic can add a new dimension to battles and problem - solving, like using the force of a magic bullet to break through powerful enchantments.
Well, Morrigan Aensland might be a powerful ally from another dimension. Suppose there is a greater evil emerging in the Harry Potter universe that the regular wizards are ill - equipped to handle. Morrigan, with her different brand of magic and combat skills, could step in. She could teach the students new ways of defending themselves, perhaps a more aggressive form of magic compared to what they're used to. Her presence would also shake up the existing power structures at Hogwarts and in the wizarding world as a whole. The Ministry of Magic would be both suspicious and in awe of her, trying to figure out how to deal with this new entity in their midst.
The Plague Doctor could be a magical healer from a far - off land. His strange appearance and methods are initially met with suspicion in the Harry Potter world. But as the story progresses, his skills in dealing with diseases become invaluable. For example, he could use his beak - like mask not just for protection but also as a tool to channel magic for healing.
One idea could be that Tinkerbell finds her way into the wizarding world of Harry Potter. Maybe she gets accidentally transported there by some magical mishap. She could use her fairy magic in Hogwarts, like helping to repair broken objects in a more sparkly and unique way compared to the Reparo charm.
Pikachu could be a special guest at Hogwarts. It might be brought there by a powerful wizard who has traveled to other dimensions. And it could use its electric attacks to protect the school from dark forces.
Nyssa al Ghul could be a mysterious new teacher at Hogwarts. She could teach a subject related to self - defense or ancient magic. Her skills in combat and stealth would make her a very interesting addition to the Hogwarts faculty.