One interesting crossover could be the use of magic in the world of Pirates of the Caribbean. For example, a wizard from Harry Potter might find themselves on a pirate ship and use spells to fend off sea monsters. Another could be the pirates trying to steal magical artifacts from the wizarding world.
Well, in a crossover, the ponies could have a ship of their own, like a flying ship made of clouds or something really magical. They could cross paths with the pirates during a storm. The ponies' ship could be immune to some of the bad weather effects because of their magic. And then they team up with the pirates to find a hidden treasure that requires both the pirates' seafaring skills and the ponies' magic.
One good crossover could be Percy using his water - controlling abilities in the world of Pirates of the Caribbean. For example, he could help Jack Sparrow's ship escape from a powerful maelstrom by calming the waters. Another idea is Percy teaming up with the pirates to fight against a common sea - based enemy, like a giant sea monster that威胁 both the demigod world and the pirate world.
There might be a fanfiction plot where Elizabeth Swann, instead of being a damsel in distress at times, becomes a powerful pirate captain in her own right. She could lead her own ship and crew, and have adventures that cross paths with Jack Sparrow's. For example, she might be on a quest to find a magical artifact that can control the seas and has to outwit other pirates and sea monsters to get it.
One idea could be that the RWBY characters find themselves on a cursed ship similar to the ones in Pirates of the Caribbean. Ruby could be the fearless leader, using her scythe in sword - fights on the ship's deck. Weiss might be the one trying to figure out the magic or curses involved, with her knowledge of Glyphs. Blake could use her stealth skills to explore the ship and discover hidden secrets, and Yang would be the muscle, ready to take on any enemy pirates.
One idea could be a crossover with 'Peter Pan'. The pirates could sail to Neverland and have adventures with Peter, Tinker Bell and the Lost Boys. Maybe Captain Jack Sparrow would try to steal the fairy dust from Tinker Bell.
Well, in some fanfiction, we might see Anna and Kristoff visiting Hogwarts. They could be amazed by the moving staircases and magical creatures. In reverse, Harry, Ron and Hermione could end up in Arendelle. Hermione might be intrigued by the way Elsa controls her ice powers and try to find a scientific or magical explanation for it. Also, the Dementors from Harry Potter could be compared to the dark forces in Frozen 2, like the mist that Elsa has to face.
One interesting crossover could be the use of magic in the Avengers world. For example, Hermione could use her knowledge of spells to help the Avengers solve a problem that technology couldn't. Maybe she could use a spell to break through an impenetrable force field created by an enemy. Another aspect could be the Avengers characters learning magic. Tony Stark might be fascinated by the concept of magic and try to incorporate it into his technology. Or Thor could share his knowledge of Asgardian magic with the Hogwarts students.
One interesting crossover could be a scenario where Hermione uses her magic to help Elsa control her powers better. Maybe she creates a spell that can soothe Elsa when she's about to lose control.
In some fanfiction, Maleficent might team up with a dark wizard from the Harry Potter universe. They could combine their powers to try and take over both the wizarding world and the fairy - tale land where Maleficent comes from. This would create a complex power struggle with the heroes having to find new ways to combat them.
One interesting crossover could be the characters from Harry Potter visiting Narnia. For example, Harry, Ron, and Hermione might find themselves in Narnia through some magical accident. They could then interact with the talking animals and magical beings there, like how they interact with the magical creatures in their own wizarding world. Maybe they would help the Narnians in a battle, using their unique Hogwarts - taught magic.