A possible crossover could be that Balto is a form of Animagus. In the 'Harry Potter' universe, some wizards can transform into animals. Balto could be an Animagus who was born in the wizarding world but got lost in the Muggle world. When he returns, he has to adapt to the wizarding ways again.
A possible crossover could be the use of Zoids in Quidditch. Imagine a Zoid - powered Quidditch match where the players ride Zoids instead of broomsticks. It would be a high - energy and very different kind of game.
There could also be a crossover in terms of the settings. Shazam could bring some of his city - based heroic adventures into the wizarding world. So instead of just the streets of his city, he's now running around Hogwarts, using his powers to solve mysteries that are related to both the magical world and his own world of superheroes. This could create a whole new set of adventures for both him and the Harry Potter characters.
A possible crossover could be in the area of magic. The Addams family might have their own brand of 'weird' magic that clashes or combines with the magic in Harry Potter. For instance, Pugsley Addams could create some really odd potions using ingredients from both the Addams' world and Hogwarts' supply.
In a 'harry potter is a jinchuuriki fanfiction', a crossover might involve the social aspects. In the Naruto world, jinchuuriki are often ostracized. Harry, already an outcast in the wizarding world, could experience a different kind of ostracization or acceptance based on his new status as a jinchuuriki. His friends might react differently to him having this new power within him, and there could be a whole new dynamic in his relationships. Also, the training methods for jinchuuriki could be incorporated into how Harry trains to become stronger, mixing the physical and mental training from Naruto with the magical training in Harry Potter.
Well, one possibility could be the use of magical spells in a shinobi - like combat. For example, Harry Potter's spells like 'Expelliarmus' could be used in a fight against shinobi enemies, perhaps disarming them of their ninja tools. Another could be the idea of Hogwarts students learning shinobi skills like stealth and parkour. It would be really interesting to see how the two different worlds of magic and ninjutsu could blend together.
One possible theme could be friendship. Maybe the angry unicorn initially has a conflict with Balto but then they become friends.
A crossover with the Narnia series is also possible. Harry might be a servant in the magical land of Narnia, serving one of the kings or queens there. Maybe he could be helping with magical tasks that are specific to Narnia's brand of magic.
One interesting idea could be a crossover with 'Lord of the Rings'. Imagine Harry and his friends in Middle - earth, facing the dark forces there. They could learn new magic from the wizards in Middle - earth or teach their own brand of magic. Another idea is a crossover with 'Percy Jackson'. The demigods and the wizards could team up to fight a common enemy that threatens both the magical and the mythological worlds. Maybe they'd have to combine their powers and strategies.
One interesting crossover could be the use of Stargate's technology in the Harry Potter universe. For example, the Stargate could be a magical object that transports wizards to different wizarding worlds or even other planets. Another idea could be that some Stargate characters end up at Hogwarts and have to learn magic to survive. They might introduce their own technology and knowledge, creating a whole new dynamic within the school.
One interesting crossover could be the use of magic in the Avengers' world. For example, Harry Potter characters could teach the Avengers some basic spells to help them in their battles. Another aspect could be the characters' personalities interacting. Hermione might befriend Bruce Banner and they could exchange knowledge about science and magic.