One interesting crossover could be the magic systems. For example, imagine if the hobbits had access to some of the more unique spells from the Harry Potter universe, like the Patronus charm. It could be used to protect them from the various evils in Middle - earth.
In some fanfictions, the One Ring could have an impact on Naruto characters. Suppose the ring's power of corruption was tested on Naruto or Sasuke. How would they resist its allure? Also, the hobbits' simple and brave nature might remind Naruto of his own friends in Konoha, leading to some interesting cultural exchanges in the fanfiction.
One interesting 'Harry Potter Hobbit Fanfiction' story could be one where the characters from 'Harry Potter' end up in Middle - earth from 'The Hobbit'. For example, Harry Potter and his friends might encounter hobbits and dwarves and have to work together to face a new dark force. They could use their magic in ways that the people of Middle - earth have never seen before.
One interesting crossover could be the characters from Percy Jackson ending up in Middle - earth from The Hobbit. For example, Percy using his water powers in the rivers of Middle - earth. It would be a cool way to see how his abilities interact with the new environment.
One interesting plot could be that the wizards from Harry Potter world accidentally stumble upon the Shire while on a magical experiment gone wrong. They meet the hobbits and learn about their simple yet fulfilling lives. Meanwhile, the hobbits are in awe of the magic the wizards possess. Then, an ancient evil that threatens both the wizarding world and Middle - earth emerges, forcing them to combine their strengths. The wizards use their powerful spells and the hobbits' courage and resourcefulness to fight against it.
There could also be a scenario where Harry Potter has to face the Joker in a psychological battle. Since Harry has faced his own share of dark forces, the Joker's mind - games could be a new and different kind of challenge for him. Harry would have to use his courage and the skills he learned at Hogwarts to outwit the Joker.
A really interesting crossover is when the magic of Harry Potter is used to enhance the gadgets in Kingsman. For example, in some fanfics, they create wands that can also function as Kingsman umbrellas, with the ability to both shoot spells and act as a shield or a parachute. It's a cool blend of the two worlds' technologies.
Another interesting crossover is when the Deathly Hallows are somehow connected to the tailed beasts in Naruto. It's a unique take that combines the powerful artifacts from Harry Potter with the equally powerful beasts from Naruto. This often leads to a story full of high - stakes battles and unexpected alliances.
One interesting crossover could be the use of magic in the Warframe universe. For example, a Harry Potter character might bring spells like 'Accio' to retrieve items in the middle of a Warframe mission. Or perhaps a Warframe with magical abilities inspired by Hogwarts magic.
One interesting crossover could be a Creepypasta character infiltrating Hogwarts. For example, Jeff the Killer could be lurking in the Forbidden Forest, adding a terrifying element to the otherwise magical place. It would be a really spooky scenario as students unknowingly get closer to this dangerous figure during their adventures in the forest.
One interesting crossover could be a scenario where Alucard uses his vampiric powers to assist Harry in a battle against Voldemort. Maybe Alucard's super strength and ability to transform could give Harry an edge in a difficult fight.