Well, think about a scenario where the Philosopher's Stone gets stolen and taken to Asgard. Harry, Ron, and Hermione follow it there. Thor, initially suspicious of these strange wizards, eventually realizes they are on the same side. Together, they embark on a quest to retrieve the Stone, with Thor providing his brute strength and the Hogwarts gang using their wits and magic along the way.
One interesting crossover could be Darkseid's quest for the Deathly Hallows. Imagine him believing that these powerful magical artifacts could enhance his already great power. He might send his minions to Hogwarts to search for them, leading to a battle between the students and Darkseid's forces.
A possible crossover might involve Aragorn being magically transported to Hogwarts. He could be a bit bewildered at first by all the magic around him, but then he starts to adapt. He might end up training the students in physical combat skills, which are lacking in the wizarding world. Meanwhile, Harry Potter could be fascinated by Aragorn's tales of his adventures in Middle - earth and might even try to incorporate some of Aragorn's courage and honor into his own life.
One interesting crossover could be the Quirk vs Magic aspect. In many bnha harry potter fanfictions, characters from BNHA like Deku might visit Hogwarts and try to understand magic while the Hogwarts students are fascinated by his Quirk. It makes for a great exploration of two very different power systems.
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.
One interesting crossover could be Ben using his alien forms to help the students at Hogwarts during a dark wizard attack. For example, his Heatblast form could be useful against ice spells. Another could be Harry Potter using magic to enhance Ben's Omnitrix. Maybe a spell that makes it transform faster or unlock new alien forms.
One interesting crossover could be the use of magic from Harry Potter in the RWBY universe. For example, a character from RWBY might learn how to use spells like Wingardium Leviosa to help in combat or daily tasks. Another could be the Hogwarts houses being applied to RWBY characters, with Ruby perhaps being a Gryffindor due to her bravery.
In some Harry Potter and Riverdale fanfiction, the houses in Hogwarts could be compared to the social groups in Riverdale. For example, Gryffindor's bravery could be related to how the Bulldogs in Riverdale stand up for what they believe in. Slytherin's cunning might be similar to how some of the more devious characters in Riverdale operate. And then there could be a plot where characters from Riverdale are sorted into Hogwarts houses and have to adapt to the new environment based on the traits of their houses.
In Harry Potter and Clannad fanfiction, a great crossover idea is the exchange of character traits. Maybe some of the Clannad characters could be sorted into Hogwarts houses based on their personalities. And vice versa, the Hogwarts students could learn about the strong family and friendship bonds in Clannad. It could also involve a plot where a powerful Clannad character has to deal with the dark magic threats in the Harry Potter universe. This would create a whole new set of challenges and adventures for both sets of characters.
One interesting crossover could be the use of magic systems. For example, how would the Shadowhunter runes interact with Harry Potter's spells? Maybe a character from the Shadowhunter world could find themselves at Hogwarts and be both amazed and confused by the different forms of magic. Another aspect could be the characters' personalities clashing or working together. A brave Gryffindor and a fearless Shadowhunter might team up to fight a common evil that threatens both their worlds.
One interesting aspect could be the contrast in magic systems. In Harry Potter, magic is more about spells and potions, while Starscream has his own set of technological 'powers' in the Transformers universe. A crossover might explore how they interact. For example, how would Starscream react to a wizard's ability to apparate? And how would a wizard deal with Starscream's flight and weaponry capabilities.