Perhaps a fanfiction where a young witch or wizard from Hogwarts has a natural affinity for Storm's powers. They could be an outcast at Hogwarts because of their different abilities. But when a great danger looms over both the magical world and the world of Storm, they are the key to bringing both sides together. Their unique combination of magic and Storm powers helps to save the day in a very unexpected way.
A possible fanfiction could involve a time - travel scenario. Tony accidentally travels back in time to the era of Harry Potter. He realizes that he can use his knowledge to prevent some of the tragedies in the wizarding world. He partners with Harry and uses his Iron Man suit's capabilities along with magic to change the course of events.
One idea could be that Azula, with her firebending skills and strategic mind, is somehow transported to the Harry Potter universe. She could be sorted into Slytherin and form an unlikely alliance with Draco Malfoy. They might plot together to gain power within Hogwarts, using Azula's manipulation tactics.
A third idea is a time - travel based fanfiction. Elsa somehow gets sent back in time to the era of Harry Potter's parents. She uses her powers to save them from Voldemort, which changes the entire future of the wizarding world. Harry then meets Elsa in his own time, and they have to figure out how her actions in the past have altered the present and what they can do to keep the peace in this new, changed world.
A fanfiction could revolve around a powerful demon who has been trapped in the wizarding world for centuries. Harry Potter and his friends come across this demon and find out that it holds the key to defeating a new, even greater dark force that is threatening both the wizarding and muggle worlds.
One idea could be that Sesshomaru somehow gets transported to the Harry Potter universe. He might initially be confused by the magic there which is different from his own demonic powers. He could encounter Harry and be both intrigued and a bit disdainful, seeing Harry as a young, inexperienced wizard compared to his own powerful self. But as time passes, they might have to team up to fight a common enemy that threatens both the wizarding world and Sesshomaru's own interests.
One idea could be to have the characters from Harry Potter world attend the Vongola Academy in the KHR universe. They could learn about the different flames and how to use them while also sharing their magical knowledge. For example, Hermione would be really interested in the scientific aspects of the Dying Will Flames and might try to find a way to combine it with her magic.
In 'Harry Potter x Pokemon fanfiction', an interesting concept could be the magical creatures in the Harry Potter universe interacting with Pokemon. For instance, the Hippogriffs could befriend Flying - type Pokemon, and the Centaurs could have some sort of relationship with Grass - type Pokemon. Also, the spells in Harry Potter could have an impact on Pokemon. Maybe the Stupefy spell could temporarily paralyze a Pokemon, and the Protego spell could protect against a Pokemon's attack. This would create a whole new dynamic between the two universes, and characters from both worlds would have to adapt to these new interactions.
One idea could be that McGee discovers he has a hidden magical ability and is sent to Hogwarts. There he meets Harry Potter and they become friends. McGee could use his Muggle knowledge in unexpected ways in the wizarding world.
One idea could be a crossover where Noctis visits Hogwarts. He could be mistaken for a new kind of wizard with his unique powers. Maybe he gets sorted into a house, like Gryffindor for his bravery, and then he has to learn about magic in the wizarding world while also sharing his own skills with the students.
One idea could be that Hogwarts students visit Pandora. They could learn about the unique magic of the Na'vi, like their bond with the animals. Maybe a Hogwarts professor is intrigued by the Eywa and wants to study it. Another could be a character from Harry Potter getting lost in Pandora and having to adapt to the Na'vi way of life while also using their own magical skills to survive.