A fanfiction could also revolve around a scenario where Naruto's world is in danger of being destroyed by an interdimensional threat. Doctor Strange, sensing this from his own universe, travels to Naruto's world. He then helps Naruto unlock a new level of power within himself, perhaps by teaching him how to use his chakra in a more magical and controlled way. In return, Naruto teaches Doctor Strange about the importance of friendship and loyalty in combat, which is a big part of the ninja way.
One idea could be that Naruto is somehow transported to the Marvel universe and meets Doctor Strange. Doctor Strange could sense Naruto's unique chakra and be intrigued. He might offer to train Naruto in new forms of magic that are similar to his jutsu. Naruto, in turn, could show Doctor Strange some of his ninja skills, like his shadow clone jutsu which could be useful in combat situations in the Marvel world.
One idea could be a crossover where Doctor Strange uses his magic to visit the wizarding world of Harry Potter. He could meet Harry and help him with some of his more difficult magical problems, like dealing with a particularly powerful dark magic spell that the Hogwarts professors are stumped by.
Another possibility is a story in which a young wizard in the Harry Potter world discovers a hidden portal that leads to the dimension where Doctor Strange operates. This wizard, inspired by Strange, begins to study a new form of magic that combines the principles of both universes. They then return to Hogwarts and start to teach their friends this new hybrid magic, which causes quite a stir among the faculty and students alike.
Perhaps in the fanfiction, Harry Potter gets lost in the multiverse and ends up in the world where Stephen Strange operates. Strange takes Harry under his wing, teaching him about the different forms of magic beyond what he knows from Hogwarts. Harry, in turn, could introduce Strange to some of the more unique magical creatures from his world, like the Hippogriff.
One idea could be to have characters from Naruto end up in the world of Danmachi. For example, Naruto himself could find his way into the dungeon and his ninja skills would be put to the test against the dungeon monsters. His shadow clone jutsu could be used in interesting ways, like sending clones into different dungeon levels to scout or fight. Another idea is to have the concept of chakra introduced into the Danmachi world. This could change the way adventurers fight and level up. Maybe some of the Naruto characters could train the Danmachi adventurers in new combat techniques.
One idea could be a crossover where Naruto is somehow transported to the Star Wars universe and meets Padme. Maybe he uses his ninja skills to protect her from the Sith.
Another concept is that Naruto is sent to Middle - earth. There, he could use his ninja skills and chakra powers. He and Gandalf could team up to fight Sauron. Naruto's ability to make friends and inspire others would be really useful in uniting the different races of Middle - earth against the common enemy.
A more complex idea is that the Matrix is used to create a virtual training ground for the shinobi. They enter the Matrix to practice their skills in a more controlled environment. However, they soon realize that there are some dark secrets within the Matrix, and Naruto has to lead the way to uncover the truth and free those who are trapped inside.
Another possibility is that Naruto visits the Townsville, the city where the PPG live. He might be confused by the modern technology there compared to his own world. The PPG could teach him about it while he shows them some of his ninja skills like tree - climbing and water - walking.
A third idea could be a story where Naruto's clones are mistaken for some kind of superpower by the Thundermans. Max might be intrigued and try to figure out how to do it himself. Meanwhile, the Thundermans could teach Naruto about modern technology which he has never seen in his own world. This could lead to some really interesting and comical situations as they try to understand each other's worlds.
Another possibility is that Pokemon exist in the Naruto world. Some ninja could have Pokemon as partners instead of traditional ninja animals. For example, Sasuke could have a Dark - type Pokemon like Umbreon that would match his cool and mysterious personality. And the Pokemon battles could be incorporated into the ninja battles, adding a new layer of strategy.