A giant eagle would be really cool. It could carry Naruto around and give him a great view of the land. Also, a wise old turtle that might have some ancient knowledge to share.
In this fanfiction, Naruto might interact with a talking snake. Snakes are often associated with mystery and danger in the Naruto universe, so it would be a very engaging interaction. A group of intelligent monkeys could also be really interesting. They could be mischievous but also very helpful in certain situations. And how about a unicorn - like horse? It would be a beautiful and powerful animal that Naruto could form a special bond with, perhaps using its speed and magic - like abilities in battles or quests.
Well, it could enhance his relationships. For example, his friends might be amazed and find it really cool. It could also make some characters jealous. And it might lead to new alliances as he can communicate with animals that others can't, so he could get help from them in battles or other situations.
The unique perspectives. We get to see the Naruto world from the animals' point of view. For example, how they feel about being summoned by ninjas. It adds a whole new layer to the story.
I think Mewtwo would be the most fascinating for Naruto to talk to. Mewtwo is a very intelligent and powerful Pokemon. It has complex thoughts about its existence and purpose. Naruto, with his own struggles and growth in the ninja world, could have deep philosophical discussions with Mewtwo. They could exchange ideas about power, identity, and what it means to be different in their respective worlds.
Sasuke would be really interesting. His relationship with Naruto was always complex, and if Naruto is a girl, it could add a new level of tension or even a different kind of friendship/rivalry. Sakura too. She might have a whole new perspective on Naruto as a girl, and they could form a stronger bond as female comrades. And Kakashi, his reaction to Naruto's transformation could be quite humorous and also a source of guidance for Naruto in this new situation.
In this fanfiction, Naruto would interact with a variety of characters. First, his old friends like Choji and Kiba. They have been through a lot together and would support Naruto in the war. Then there are the leaders of the different ninja villages. Naruto might meet with the Raikage or the Mizukage. His interactions with them could range from tense negotiations to forming alliances. And don't forget about Hinata. Her support for Naruto could be a source of strength for him during the difficult times of war.
In Naruto fanfiction, a lot of creative animal partners can be found. For example, there could be a magical dolphin that can swim through the air as well as water. It could be used to quickly transport the ninja across long distances. Another idea is a phoenix - like bird that can resurrect from its ashes and provide protection to its partner in the form of a fire shield. And then there's the possibility of a bear with super strength and the intelligence to strategize in battles.
Iron Man is another candidate. Tony Stark's technology and Naruto's ninja techniques could be a great contrast. They could learn from each other. Stark might be interested in Naruto's chakra - based powers and try to replicate them in some way, while Naruto could be amazed by Stark's high - tech gadgets.
Obviously, Naruto himself is a main character. He will be interacting with the Kyuubi. Since the Kyuubi is a powerful and sentient entity within Naruto, their interactions could be intense. Naruto might also encounter other ninja who have knowledge about the Kyuubi. For example, Jiraiya. Jiraiya, being Naruto's mentor, might appear to give advice on how to handle the situation with the Kyuubi. He could share some of his own research and experiences related to the tailed beasts.
Jiraiya. Naruto could have a different kind of apprenticeship with Jiraiya. He could share some of his future experiences with Jiraiya, which might change how Jiraiya trains him and also how Jiraiya approaches his own missions and prophecies.
One of the most interesting could be the ghost of the First Hokage. He has so much knowledge about the founding of the village and the early days of the ninja world. Naruto could learn a great deal from him, like how to better lead and protect the village.