Naruto might run into an alternate Itachi. In this AU, Itachi could be alive and not have committed the atrocities he did in the original story. He could be a mentor figure to Naruto, teaching him new ninja techniques and strategies. Also, Naruto could meet a version of Kakashi who has a completely different backstory. For instance, Kakashi could be from a different ninja village and have different skills and abilities.
In this kind of fanfiction, Naruto could meet an AU version of Orochimaru who is a good - hearted scientist. Instead of using his knowledge for evil, he uses it to heal the sick and develop new technologies for the ninja world. Naruto could also encounter AU versions of minor characters like Tenten or Rock Lee, where they have different personalities or abilities. For example, Tenten could be a master of a new type of weaponry that doesn't exist in the original Naruto world.
He could meet an AU version of Hinata who is more assertive and outgoing. Maybe she's a powerful ninja in her own right and not as shy as in the original story.
Naruto may run into some friendly space explorers who are amazed by his ninja skills. They could help him navigate the strange new world of space and introduce him to advanced technologies that are different from what he's used to in the Hidden Leaf Village. There might also be some wise, old beings in space who can teach Naruto new ways to master his chakra.
One possibility is that Naruto enters an AU where chakra doesn't exist. Instead, there are other forms of power. He would have to learn how to use this new power from scratch. Also, the relationships between different ninja clans could be very different. Naruto might end up making new alliances and enemies based on this new dynamic. This could be a great opportunity for character development as he faces challenges that are completely different from what he's used to in his original world.
Naruto would meet his younger self. This would be a really strange situation. He could also meet all the important shinobi from the past. For example, the First and Second Hokage. He might have a chance to learn from them directly, instead of just hearing about them in stories. Additionally, he could meet some of the characters who were only mentioned in passing in the original story but had a big influence in the past.
He could meet alternate versions of his friends. For instance, an alternate Sasuke who has never left the village and is a strong ally from the start. This Sasuke could be more open and friendly, and together they could face the challenges of the new universe.
There might be an old sage living in the mountains of one of the elemental nations. The sage has vast knowledge of ancient ninja arts and has been in isolation for years. Naruto's encounter with this sage could be a turning point in his journey, as the sage could offer him wisdom and perhaps even a new form of power or training method.
There could be a group of kids on the beach who are inspired by Naruto. They might approach him and ask for autographs or to show them some ninja moves. Naruto would be happy to oblige and in the process, he could discover a new talent among the kids that could be important for the future of the ninja world.
Danzo could be a great antagonist in this 'naruto highschool au fanfiction'. He could be the strict school principal who enforces very strict rules and has a hidden agenda. He might not like Naruto's free - spirited nature and try to expel him. Also, Kabuto could be a student who is under Danzo's influence and causes trouble for Naruto and his friends.
Sasuke could still be an antagonist in a way. Maybe in this AU, he's more dismissive of the female Naruto because of his own ideas about strength and gender. He might see her as weak at first and that could create a lot of tension between them.
In this fanfiction, Naruto might run into Arthas Menethil before he fully turned into the Lich King. It would be a very different kind of encounter compared to what he's used to in his own world. He could also meet Uther the Lightbringer. Uther might be curious about Naruto's unwavering will and Naruto could be in awe of Uther's connection to the Light. Additionally, he could meet many of the adventurers and common folk in Azeroth, each with their own stories and skills.
Maybe some local tribespeople who have unique abilities or knowledge. For example, they could teach Naruto some ancient techniques or survival skills that are not known in the Hidden Leaf Village. There might also be wandering samurai or other shinobi from different regions who pass by the outpost and interact with Naruto.