A third idea could be a story where a young wizard from Hogwarts discovers an ancient connection to the world of Eragon. They accidentally stumble upon a portal that leads to Alagaësia. There, they befriend Eragon and learn about a different kind of magic. This could lead to the wizard bringing some of the knowledge of dragon riding and Alagaësian magic back to Hogwarts, changing the way magic is taught and understood there.
One idea could be a magical exchange program. Wizards from Hogwarts and Dragon Riders from Alagaësia meet and learn from each other's magical systems. Harry Potter characters could be fascinated by the bond between Eragon and his dragon Saphira, while Eragon might be intrigued by the variety of magic at Hogwarts like Transfiguration and Potions.
Maybe a dark force threatens both worlds. Voldemort somehow discovers the power in Alagaësia and tries to use it for his own evil purposes. Eragon and Harry team up, along with their friends, to fight against this new threat. The wizards use their spells and the dragon riders use their combat skills and dragon powers to combat this common enemy.
One idea could be that Eragon, while on one of his adventures in Alagaësia, accidentally creates a portal that leads him to Hogwarts. There, he meets Harry Potter and they quickly realize they have a lot in common. They could team up to fight against a dark force that somehow threatens both their worlds, like a new type of dark magic that combines the magic of Alagaësia and the dark arts from the wizarding world.
One idea could be a crossover where characters from both universes meet. For example, Harry Potter could encounter Eragon and they could learn from each other's magic systems. Maybe Harry could teach Eragon about some of the more complex spells in the wizarding world, while Eragon shows Harry how to bond with a dragon in a more in - depth way.
One idea could be that Merlin, with his magic from the Arthurian world, meets Eragon in Alagaesia. Maybe Merlin helps Eragon to better understand and control his own magic, as Merlin has centuries of experience. He could teach Eragon about different forms of magic and how to use it more subtly.
Well, perhaps Eragon's dragon, Saphira, is injured and they have to seek out the healing magic in Skyrim. Along the way, they meet the Dragonborn. The two dragon - related characters could either become friends or rivals. Eragon might be amazed at the variety of dragons in Skyrim, some of which are different from the ones he knows. And he could share his knowledge of dragon - riding with the Dragonborn.
One interesting crossover could be the use of magic systems. In some fanfictions, the characters might combine spells from Harry Potter with the dragon - related magic in Eragon. For example, a wizard from Harry Potter might learn to communicate with dragons like the characters in Eragon.
Another possibility is that Voldemort somehow discovers the world of Narnia and tries to conquer it. This would force the Narnian characters to team up with the Order of the Phoenix. Harry Potter and his friends could learn about the talking animals and different forms of magic in Narnia, while the Narnian heroes would see the power of wizardry. It could lead to a great adventure full of battles and new friendships.
A cool Harry Potter OC Crossover Fanfiction idea could be to have an OC crossover with the world of Middle - earth. Imagine an OC from Hogwarts traveling to Middle - earth and using their magic to help in the battles against Sauron. They could introduce wands and spells to the hobbits and elves. Also, a crossover with the world of Fairy Tail would be interesting. The OC could join the Fairy Tail guild and participate in their quests while also showing off the unique magic of the Harry Potter universe. And a crossover with the world of Howl's Moving Castle could be fun too. The OC could interact with Howl and Sophie and learn about their form of magic which is different from Hogwarts magic.
One idea could be having Harry Potter characters attend an anime - style magic school in Japan. For example, Harry could be a transfer student to a school where they teach magic in a very different way compared to Hogwarts, with elements like anime - inspired uniforms and more focus on martial arts - based magic.
Perhaps there could be a magical object in 'Harry Potter' that is somehow related to the werewolves in 'The Howling'. For example, a spell book that has the secrets to controlling werewolf transformations. The characters from both worlds could be on a quest to find this book and in the process, they learn more about each other's worlds and how magic works differently in each.
A great idea for 'harry potter and friends crossover fanfiction' is a crossover with 'Narnia'. The magical world of Narnia and Hogwarts have some similarities. Harry and his friends could enter Narnia through a magical portal in Hogwarts. They could help the Pevensie children in their battles against the White Witch. Another option is a crossover with 'The Chronicles of Prydain'. Harry and his friends could journey to Prydain and encounter the magical creatures and challenges there. And a crossover with 'Fantastic Beasts' but in a different way, like the main characters from 'Harry Potter' meet Newt's ancestors and have adventures with them.