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.
One idea could be a crossover where Thor somehow ends up in the Star Wars universe during the Clone Wars. Maybe he's on a mission from Asgard to find a powerful artifact that has been lost in this strange new galaxy. He could team up with the Jedi, and his god - like powers would be a huge asset in the battles against the Separatists.
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.
Perhaps a fanfiction where some of the Naruto characters are actually clones themselves, like in The Clone Wars. Naruto could be a special clone created with a combination of chakra and the Force. His purpose could be to bring peace between the two universes. Hinata could be a healer in this new world, using her gentle nature and Byakugan to sense injuries and use the Force to heal them. This would mix the two universes in a unique way and create a lot of new storylines.
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 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.
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.
Another fanfiction concept could involve Jedi and Sith being reincarnated on Earth. They'd have to adapt to modern society while still holding onto their powers and the eternal struggle between the light and dark side. For example, a young Jedi might discover their powers in a world full of distractions and temptations, and they'd have to learn how to use them for good.
One idea could be to have Danny Phantom's powers in the Star Wars universe. For example, he could use his intangibility to sneak past stormtroopers or his ghostly energy blasts as a new type of weapon. Maybe he gets caught in a wormhole and ends up in a galaxy far, far away and has to find his way back home while getting involved in the Galactic Civil War.
One interesting plot idea could be exploring Dooku's early days in the Sith. Maybe showing how he was gradually corrupted by Sidious. Another could be a story where Dooku has a change of heart briefly and tries to make amends in some small way during the Clone Wars, but is quickly pulled back into the dark side by Sidious' influence. A third idea could be a fanfic that focuses on Dooku's relationship with his former Jedi colleagues during the Clone Wars, like how he feels when facing them in battle.