One idea could be a Moana crossover with Frozen. Moana could end up in Arendelle due to a magical storm. She teams up with Elsa and Anna to stop an approaching iceberg that is threatening both her island and Arendelle. Moana's skills in sailing and her connection with the ocean could be combined with Elsa's ice powers to find a solution.
Imagine a fanfiction where Moana and the Little Mermaid embark on an adventure to a mysterious island in the middle of the ocean. This island is said to hold the key to a powerful magic that can heal any damage to the ocean. Moana would be excited to explore the island, while Ariel would be a bit more hesitant as she is used to the underwater world. But once they land, they discover that the island is full of strange and wonderful things. They meet creatures that are part - plant, part - animal, and they have to solve puzzles to get closer to the magic. Their different perspectives and skills would make this a thrilling and unique adventure.
It could be about Naruto somehow ending up in Moana's world. Maybe he uses his ninja skills to help Moana on her journey to save her island. For example, Naruto could use his shadow clone jutsu to do multiple tasks at once like helping to repair damaged parts of the island while Moana focuses on finding the heart of Te Fiti.
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.
One possible plot could be that Moana's island is threatened by dark magic from the Harry Potter universe. Harry, Hermione, and Ron could be transported to Moana's world while on a mission to stop the spread of this dark magic. They would team up with Moana to use her knowledge of the ocean and the island's magic, along with their own wizarding skills, to fight off the dark forces. Maybe they'd have to face off against a wizard who has enchanted some of the sea monsters in Moana's world.
Obviously, Naruto and Moana would be the main characters. They are from their respective universes and would be the ones driving the story forward in a crossover. Their different personalities and abilities would create interesting interactions.
A cool plot could be that a dark force from Naruto's world has found a way into Moana's world. Naruto, with his knowledge of fighting evil, and Moana, with her knowledge of the local terrain and the ocean, must work together. Naruto might be a bit clumsy at first with the whole sailing thing, but his combat skills are invaluable. Moana, on the other hand, can communicate with the ocean to get them out of tight spots, and together they defeat the dark force.
It could be Orochimaru. Imagine he discovers the power of the ocean in Moana's world and wants to use it for his own dark experiments. He could start corrupting the sea creatures and causing chaos on Moana's island. Naruto, having faced Orochimaru before, would know his weaknesses and team up with Moana to stop him.
If it's a Moana and Hercules crossover, Hercules would be a great addition. His super strength could help Moana in situations where physical power is needed, like moving large obstacles in her path. Also, Philoctetes could be there to train Moana in some combat skills, adding an interesting dynamic to the story.