Tsunade would definitely be one. As the most renowned medical ninja in the village, she could either be Naruto's mentor or a colleague. They could exchange medical knowledge and experiences.
Sakura is another obvious choice. She is also a medical ninja. Naruto and Sakura could work together to treat patients. Their friendship could be further developed through their shared medical duties, and they might also have some friendly competitions in the medical field.
Naruto might interact with Eostia's warriors. They could train together, Naruto showing them his ninja combat skills and them teaching him about Eostia - style combat. There could also be some mysterious characters in Eostia, like an old hermit who has some knowledge about Naruto's sudden appearance in their world and could guide him on his journey in Eostia.
In a crossover with the Attack on Titan world, characters like Eren could interact with Naruto. Eren, with his strong will to fight for freedom, could learn from Naruto's experience as a father and a hero. Levi might also be interested in Naruto's combat skills and how he trains his child in the ways of the ninja.
He could interact with Mei Terumi, the Mizukage. She might be initially cautious of Naruto but then see his potential and work with him. Also, Chojuro, as he is one of the important ninjas in Kiri. They could train together or go on missions side by side.
Well, Kakashi could play an important role. Since he was Naruto's mentor, he would be very curious about Naruto's sudden change to a nobody. He might secretly investigate what caused this. Shikamaru could also interact with Naruto. Shikamaru is smart and observant. He might notice some small details about Naruto that others miss, and try to figure out the mystery behind Naruto becoming a nobody. Also, Rock Lee could be in the story. Lee might see Naruto as a new opportunity to spread his 'youth' spirit, not knowing Naruto's past.
Ruby Rose for sure. She's the main character in Remnant and Naruto would likely be drawn to her energy and determination. He could also interact with Weiss Schnee. Naruto might be interested in her family's power and wealth, and Weiss could be curious about Naruto's strange abilities. Another one could be Blake Belladonna. Given her past and her more reserved nature, Naruto might try to befriend her and help her open up more.
Sasuke could be one. He might be intrigued or even challenged by Naruto's new wild ways. Their rivalry could take on a new dimension as Sasuke tries to understand what has changed Naruto so much.
He could interact with Ichigo from Bleach. Since Naruto is in a godlike state, their encounter would be really intense. Ichigo might be both in awe and on guard against Naruto's overwhelming power.
Sasuke could be one of the main characters to interact with Dark Naruto. Given their complex relationship in the original Naruto series, Sasuke might be either drawn to help Dark Naruto because of their shared past, or he could see Dark Naruto as a threat to his own goals and power. They could have some intense battles or deep conversations about the nature of power and the path they've both chosen.
In this fanfiction, Naruto could come across some of Kumo's young shinobi trainees. He could inspire them with his never - give - up attitude. And there's a chance he'll meet some of the village elders in Kumo who might have different views on how to deal with him, either seeing him as a potential asset or a liability.
In 'naruto as a cat fanfiction', Jiraiya could be an interesting character to interact with Naruto as a cat. He might see some potential in this cat - form Naruto for some new ninja techniques. The Akatsuki members could also interact with Naruto as a cat. For example, Itachi might sense something unusual about this cat when he passes through the village. And Konohamaru could be another character. He would be really excited to have a cool cat friend, not knowing it's Naruto.