One idea could be to have a wizard from the Harry Potter universe accidentally end up in the Star Wars Rebels' galaxy. Maybe they use their magic to help the rebels in unexpected ways, like creating magical shields or using apparition to outmaneuver the Empire's forces.
A more complex fanfiction could involve a group of Hogwarts students who discover a hidden portal that leads them to the world of Star Wars Rebels. They then have to adapt to the new technology while also sharing their magical knowledge with the rebels. For example, they could teach Ezra how to use a wand to perform basic spells, which he could then incorporate into his Jedi training.
One idea could be to have Naruto characters in the Star Wars Rebels universe. For example, Naruto could be a Jedi - like figure with his chakra being similar to the Force. He could use his shadow clone jutsu in battles against the Empire, creating distractions and overwhelming opponents. Sasuke could be a Sith - like character who is initially on the wrong side but later sees the light.
One idea could be a crossover where the Rebels' technology somehow gets mixed with Halo's. For example, the Rebels might discover a Halo ring and try to figure out its purpose while also dealing with Covenant forces. Maybe Ezra could use his Force abilities in new and unexpected ways against the alien threats.
One idea could be a smuggler who has a magical item from the Harry Potter world and is trying to sell it in the Star Wars universe. Maybe it's a powerful wand that could be used as a unique weapon or tool in the hands of a Star Wars character.
Maybe there's a crossover where Voldemort teams up with a Sith Lord. They could share their knowledge of dark magic and the dark side of the Force. This would create a powerful and terrifying alliance. The heroes from both universes, like Harry Potter and the Jedi, would then have to join forces to stop them. They would face many challenges as they try to understand and combat the combined powers of their enemies.
A more complex fanfic could involve characters from both universes being transported to a new world. Harry Potter characters could find themselves in the middle of the Clone Wars and have to adapt. Hermione might use her knowledge to help the Jedi understand new ways of combat or magic, while the Jedi could teach her about the Force. And Anakin could be intrigued by the magic of the wizarding world and try to incorporate it into his fighting style.
Well, you could have a fanfiction where the clones from The Clone Wars are sent to the Harry Potter universe. Imagine them having to adapt to a world without blasters and droids, but with wands and magical creatures. They might be enlisted by the Ministry of Magic to fight against a new dark force that is a combination of the Sith's evil and some dark magic that has been awakened. It would be really cool to see how they'd interact with the Hogwarts students and teachers.
One idea could be a crossover where Palpatine somehow ends up in the Harry Potter universe. Maybe he tries to use the magic there to gain more power. He could attempt to manipulate the Ministry of Magic, much like he did with the Senate in Star Wars.
One idea could be to have Sekirei characters possess unique Force abilities. For example, a Sekirei might be able to use the Force to enhance their physical combat skills in a way similar to their natural powers in the Sekirei universe. They could be part of a new Jedi order or Sith group in the Star Wars galaxy.
One idea could be a story where the XCOM 2 soldiers are transported to the Star Wars universe. They could use their advanced tactics and technology to fight alongside the Rebel Alliance against the Empire. For example, their psionic abilities could be seen as a new form of the Force by some in the Star Wars world.
There are some really interesting crossovers in the fanfiction world. One might imagine Jedi from Star Wars Rebels visiting Hogwarts in the Harry Potter universe. It could be a great story where the Force meets magic.