Some unexpected characters for the crossover could be the Powerpuff Girls. They could use their superpowers to help protect Hogwarts from dark forces. Then there's the Mad Hatter from Alice in Wonderland. His insanity and unique view of the world could bring a new perspective to the characters in Harry Potter. Also, Godzilla. Although it seems very out of place, his massive size and destructive power could be a threat that the wizards have to deal with in a very different way than they're used to.
One idea could be a crossover with the world of Narnia. Harry and his friends could accidentally stumble into Narnia through a magical portal. They would then have to adapt to the new world, deal with the White Witch, and maybe use their own magic to help the Narnians. Another plot could involve a crossover with the Lord of the Rings. The Hogwarts students could be transported to Middle - earth to help in the fight against Sauron. They could use their unique spells and magical abilities in battles against orcs and other dark forces. A third idea might be a crossover with Alice in Wonderland. Harry could follow a strange magical creature down a rabbit hole and end up in Wonderland, where he has to solve the crazy riddles and deal with the mad characters while also trying to find his way back to Hogwarts.
Harry Potter himself is always a great character to focus on. His journey from an orphan boy to a powerful wizard is full of potential for new adventures in a fanfiction that combines with 'Once Upon a Time'. Hermione Granger is also excellent. Her intelligence and knowledge of magic can lead to interesting interactions in a merged universe. Another good one is Severus Snape. His complex past and hidden loyalties can be explored further, especially when combined with the fairy - tale elements of 'Once Upon a Time'.
Filch could be an unexpected character. He might enter the tournament in a comical way, like he accidentally stumbles into the selection process and ends up being a participant. Another could be Peeves. He could disrupt the tournament in his usual mischievous way, or perhaps he is made a part of a task where the competitors have to outwit him.
One popular crossover is with the 'Lord of the Rings' universe. In these fanfics, characters might interact in various ways. For example, Frodo could meet Harry Potter and they could exchange stories about their quests against dark forces. Another is with the 'Star Wars' universe, where wizards and Jedi might have to collaborate. And then there's the crossover with the 'Percy Jackson' series. Demigods and wizards could find themselves in a situation where they need to combine their powers to face a common enemy.
She could be more empathetic as a female. Maybe she uses her intuition more in her magical studies and battles. For example, instead of just charging into a fight like the male Harry, she might first assess the situation with her heightened emotional intelligence.
Sherlock Holmes could be an unexpected character in Pinocchio crossover fanfiction. Holmes could use his deductive skills to figure out why Pinocchio's nose grows when he lies and might even try to find a way to control it. Another one could be Alice from Wonderland. Her strange adventures in Wonderland and Pinocchio's own adventures could combine in interesting ways, like exploring a new and magical land together.
Some Reddit communities can also be a great resource. Subreddits related to either 'Once Upon a Time' or 'Harry Potter' might have threads dedicated to fanfiction. You can ask for recommendations there too. Just be sure to follow the subreddit rules when posting or commenting.
One important aspect is the world - building. Since it's a crossover, the author needs to create a seamless world where the Hogwarts and the Enchanted Forest co - exist. This could involve creating new rules for how magic works when the two worlds collide. A great fanfic also respects the original source materials while adding its own unique twists. It can't just completely change the personalities of the beloved characters from 'Once Upon a Time' and 'Harry Potter' without a good reason.
One common theme is the clash of different magic systems. In both universes, magic exists but in very different forms. Fanfictions often explore how the magic from Harry Potter, like spells and potions, would interact with the magic in Once Upon a Time, which is more fairy - tale based. For example, a spell from Harry Potter might have unexpected consequences in the world of Once Upon a Time.
One underrated character is Felix. He's always by Peter Pan's side, but we don't really know much about his past or his motives. Fanfiction could explore his backstory, like maybe he was a lost boy who had a really tough life before coming to Neverland and that's why he's so loyal to Pan. Another could be the mermaids. They are often just seen as minor characters, but they could have their own complex society and relationships that could be delved into in fanfiction.