One idea could be a crossover where the characters from Monster High end up in the Naruto universe. For example, Draculaura could use her vampire powers in a unique way during a ninja battle. Maybe she can turn into a bat to avoid attacks or use her charm ability on some of the ninja opponents.
Another concept could be that some of the Naruto characters are sent to Monster High. Naruto himself might be really confused by the whole monster culture at first. He could try to use his ninja skills to fit in, like using his shadow clone jutsu to attend multiple classes at once. And his positive attitude could start to change the way some of the Monster High students view outsiders.
One idea could be a crossover where Naruto is somehow transported to the world of High School DxD. He meets Gabriel, and they team up to face a common threat. Maybe a powerful devil or a new, unknown enemy. Naruto's ninja skills could be a great asset in the battles of the DxD world.
One idea could be that Naruto is somehow transported to the world of High School DxD and meets Moka. He could use his ninja skills in the battles that take place in the DxD world. Maybe he teams up with Moka to fight off common enemies.
Another idea is that Naruto is reborn in the High School DxD world as a half - dragon due to the influence of the Dragon God. He then has to navigate the complex social and power structures of the DxD world while also hiding his true identity at first. As he discovers more about his new powers and the world around him, he gradually becomes a key figure in the battles and politics of the DxD world.
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.