One idea could be a Kakashi crossover with the Harry Potter universe. Kakashi could be a visiting wizard from a far - off magical land, teaching the students at Hogwarts some unique ninja - like magic skills. Another idea is a crossover with the DC universe. He might team up with Batman, sharing their stealth and combat expertise. A third idea could be a crossover with the Lord of the Rings world. Kakashi could be a ranger - like figure, helping Frodo and his companions on their journey with his combat and tracking abilities.
Good places to find Kakashi crossover fanfic are AO3 and Fanfiction.net. AO3 is known for its wide variety of fan - created works. You can simply type 'Kakashi crossover' in the search bar and explore the results. Fanfiction.net also has a good number of such stories. Additionally, Reddit has some Naruto - related subreddits where fans sometimes post links to their Kakashi crossover fanfics or recommend ones they've read.
One good one might be where Kakashi is betrayed in a Naruto and Harry Potter crossover. He could be betrayed by a fellow ninja who has been influenced by dark magic. In this fanfic, Kakashi might have to use his ninja skills in the wizarding world to figure out the betrayal and clear his name.
It could be an enemy who has infiltrated his team disguised as a friend. For example, in a crossover with Fullmetal Alchemist, an alchemist with the ability to change appearance might pretend to be on Kakashi's side but then betray him.
Naruto himself could be a great crossover character. Since Kakashi is his mentor in the original series, seeing them interact when Kakashi is a kid could be really interesting. They could have a different kind of dynamic, with Naruto perhaps being the more experienced one in some aspects. Another potential character is Goku from Dragon Ball. The contrast between Kakashi's ninja skills and Goku's martial arts and superpowers would create a really exciting crossover.
One common theme is power adaptation. Since Kakashi is from the ANBU, he has a certain set of skills. In crossovers, he has to adjust these skills to fit the new world he's in. For example, if he crosses into a world with magic, he might need to figure out how his ninja techniques work with the new magic system.
One common theme is the clash of cultures. Kakashi comes from the ninja world of Naruto, and when he enters the Bleach universe, there's a contrast between the two. For example, the way they handle combat and the hierarchies in their respective worlds.
One idea could be that Kakashi is somehow transported to the My Hero Academia world. He could become a teacher at UA, using his ninja skills and wisdom to train the students in new and unique ways. His Sharingan would be a very interesting power in the MHA universe.
One popular Kakashi crossover fanfiction could be a crossover with the Naruto and Harry Potter universes. In such a story, Kakashi might find himself at Hogwarts, with his unique ninja skills and Sharingan causing quite a stir among the wizards. He could potentially teach the students some new forms of combat or be involved in a battle against dark wizards.
In a Naruto Kakashi crossover fanfiction, to develop Kakashi's character, you could introduce a new love interest for him from the crossover world. This would make him open up more emotionally and show a different side of him. As for Naruto, put him in a situation where he has to teach Kakashi something. Maybe in a world where Naruto's positive attitude is the key to solving a problem that Kakashi can't figure out. This would not only show Naruto's growth but also make their relationship more equal, and both characters would be developed in new and interesting ways.