Naruto, Sasuke, and Sakura are the most obvious choices. They are the main characters and their interactions are always interesting. Naruto would bring his energetic and fun - loving nature, Sasuke his brooding intensity, and Sakura her intelligence and strong - willed personality.
Naruto himself could be in jail fanfiction. Maybe he was framed for a crime he didn't commit and has to prove his innocence from within the prison. Sasuke is also a likely candidate. His brooding and sometimes anti - social nature could lead to him getting into trouble with the law in a fanfiction setting. Another one could be Orochimaru. Given his history of unethical experiments, it's not hard to imagine him ending up in jail in a fan - created scenario.
Marinette and Adrien would definitely have an interesting interaction. Marinette is secretly in love with Adrien, and at a sleepover, there could be all sorts of awkward and cute moments between them. Maybe they end up in the same sleeping bag by accident. Alya and Nino could also have a great interaction. They're both best friends with Marinette and Adrien respectively, and they could be the ones planning all the fun activities for the sleepover. Another pair could be Chloe and Sabrina. Chloe might be her usual bossy self at the sleepover, and Sabrina would be following her around. But there could be a moment where Sabrina stands up to Chloe, which would be an interesting turn of events.
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.
Definitely Naruto and the Punisher first. Naruto would be intrigued by the Punisher's methods and would try to understand his motives. It's also possible that Sakura could interact with the Punisher. She's a strong - willed character, and she might try to either stop the Punisher if she thinks his actions are too extreme or help him if she sees the good in his goals. And Jiraiya might also be a character who could cross paths with the Punisher. Jiraiya's worldliness and his own sense of right and wrong could lead to some deep discussions between them.
Naruto is a very likely character. Given his rebellious nature and his history of being an outcast in some ways, it's easy to imagine a scenario where he gets caught up in something that lands him in prison. His determination to break free and his loyalty to his friends would make for an interesting story.
Sasuke. He has such a complex character arc and his death would have a huge impact on the story. So, in fanfiction, he's a likely candidate to come back to life and continue his journey. Maybe he has some unfinished business or a new purpose to fulfill.
Obviously Naruto himself is very likely to appear. He is the main character after all. Sasuke would also be a common character as his relationship with Naruto is so central to the story. Then there are the important figures like the Hokages, especially the ones like Minato and Hashirama who had a big impact on Naruto's life. And of course, characters like Kakashi who played a major role in Naruto's growth.
Definitely the Teen Titans. Robin would be interested in Naruto's strategic mind and combat skills. Starfire might be fascinated by Naruto's unique culture. Beast Boy and Naruto could bond over their fun - loving natures. And Cyborg would be intrigued by Naruto's chakra - based abilities compared to his technological ones.
Iruka sensei could also be very helpful. He has always been like a father figure to Naruto. He would support Naruto through this strange transformation, offering advice on how to handle the reactions of others in the village and how to adapt to this new situation without losing sight of his ninja goals.
Naruto himself is very likely to be changed. His journey to become Hokage could take a different path. Maybe he discovers his power in a more unique way or has different mentors along the way. Sasuke is also a prime candidate. His quest for revenge could be altered, perhaps he finds a different way to deal with his family's past without going down the dark path he originally did.