Another concept could be a story where Princess Zelda has some of Naruto's chakra. This chakra gives her new abilities, like being able to move at super - fast speeds or having enhanced strength. And Naruto has to train her to control this new power while they also face common enemies from both of their worlds.
One idea could be that Naruto is somehow transported to the world of Zelda. He could use his ninja skills to help Zelda in her fight against Ganon. For example, his shadow clone jutsu would be very useful for creating distractions or for gathering information in different areas of Hyrule at the same time.
Another concept is that a character from Princess Mononoke, like San, somehow ends up in the Naruto universe. She might initially be seen as a threat because of her wild nature, but Naruto could try to understand her and they could team up against common enemies like Orochimaru who is always after power and would likely be interested in the magic of the Princess Mononoke world.
One idea could be that Naruto is transported to the world of Princess Mononoke. He could use his ninja skills to help Ashitaka in his quest. Maybe Naruto's ability to make friends easily would allow him to form alliances with the different tribes in that world, like the forest spirits and the humans at Iron Town.
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.
One idea could be a crossover where Naruto characters gain the abilities of Needless characters. For example, Naruto could get the power of Adam Blade's regeneration. It would be interesting to see how he uses it in battle, especially against tough foes like Pain or Madara.