Well, it could be about Harry Potter using some Naruto - style jutsu in Hogwarts. Maybe he could learn how to do a shadow clone jutsu to help him with his studies and his adventures against Voldemort. And Naruto, if he were in the Harry Potter world, might be sorted into Gryffindor for his brave nature.
A Naruto and Harry Potter crossover with the Sharingan involved would bring a whole new dynamic. The Sharingan's powers of perception and the ability to copy techniques could be adapted in the magical realm. The fanfiction could explore how a ninja's training and skills would fare against the magic of the wizarding world. There could be a lot of cultural clashes as well. The ninjas' values and ways of life are quite different from those in the wizarding world, and this could lead to some really engaging story arcs where they learn from each other and grow.
One possible plot could be that Aquaman discovers a magical portal in the depths of the ocean that leads to the wizarding world of Harry Potter. He then teams up with Harry to fight a new threat that is endangering both the underwater kingdom and Hogwarts. Maybe it's a dark magic - using sea creature that has gone berserk.
In a Harry Potter - Moana crossover fanfiction, the magical creatures in the Harry Potter world could interact with the spirits in Moana's world. For instance, a Hippogriff could fly over Moana's island and be seen as a strange new creature. Or the Maui's fishhook could have some sort of magical connection with a powerful wand in the Harry Potter universe. The characters' personalities would also make for great combinations. Hermione's intelligence and Moana's determination could lead them to solve some big mystery together that involves both their worlds.
It could be really interesting. Maybe Harry Potter uses his magic to help Moana on her journey. For example, he could use a spell to calm the rough seas she sometimes faces. Or Hermione could use her vast knowledge to figure out some of the mysteries in Moana's world that even she doesn't understand yet.
Well, it could be about Harry Potter and his friends visiting a magical barbershop in Diagon Alley. The barbershop might be run by a wizard who uses magic scissors that can give different haircuts depending on the mood of the customer. For example, if a person is feeling adventurous, the scissors could give a wild and spiky haircut.
It could be a wizard who has gone mad with power and wants to control both the wizarding world and the underwater realm. He discovers a way to use dark magic to manipulate sea creatures and cause destruction in Aquaman's kingdom. He then sets his sights on Hogwarts as well, seeing it as another source of power.
A possible crossover could involve the magic system of Harry Potter being combined with the Gem technology in Steven Universe. For example, Hermione could study how the Gems' powers work and try to find a scientific explanation for it. On the other hand, Pearl could be fascinated by the complex spells in the wizarding world. And perhaps Dumbledore and Garnet could have a deep conversation about leadership and protecting their respective worlds.
A Harry Potter and Call of Duty crossover fanfiction might have the Hogwarts students being teleported into a Call of Duty battlefield. They would have to adapt their magic skills to the new environment. The Death Eaters could team up with the bad guys in Call of Duty. Wizards could use apparition to quickly move around the map, which would give a whole new dynamic to the typical Call of Duty gameplay.
Well, in a Tokyo Ghoul and Harry Potter crossover fanfiction, there could be a character who is both a ghoul and a wizard. This character would have to struggle with the dual nature of their existence. On one hand, they have the magic of the wizarding world, but on the other, they have the hunger for human flesh as a ghoul. They might use magic to try and control their ghoul instincts, like using a spell to suppress the urge to attack people.
A possible crossover could involve the characters from Resident Evil being transported to the wizarding world. For example, Leon Kennedy arrives at Hogwarts. He teams up with Harry Potter to fight off some dark creatures that have been infected by a strange magical - biological agent. They combine their combat skills and knowledge to overcome the threat.