Kakashi could be a good character to put in. His experience and wide range of ninjutsu could be useful in the story. For Thalia's side, Luke could be included. His conflicted nature and his skills would add a layer of intrigue, especially when interacting with Naruto and Thalia, as they try to figure out whether to trust him or not.
Annabeth would be a great addition. Her intelligence and strategic thinking could add a lot to the story. For example, in a situation where Percy and Thalia are stuck in a maze - like the Labyrinth - Annabeth's knowledge of architecture and mythology could help them find their way out. She could also create some interesting relationship dynamics, like a friendly rivalry with Thalia.
The Hunters of Artemis could be a great addition. Since Thalia was once a part of them, it would be interesting to see how she interacts with them again, especially in the context of her relationship with Percy. Zoe Nightshade, if brought back in some way, could be a very cool character to include. She has a strong personality and a tragic backstory. Also, Clarisse La Rue could be in the story. Her tough - as - nails attitude and her rivalry with Percy could spice things up, especially when it comes to the relationship between Percy and Thalia.
For a more unique take, including Jiraiya could be great. His pervy but knowledgeable personality could lead to some humorous and yet useful moments. He might have some ancient knowledge about the connection between the Naruto world and the Pokémon world where Darkrai comes from. On the Pokémon side, Cynthia could be a great addition. As one of the strongest Pokémon trainers, she could offer a different perspective on Darkrai and also help in battles against any enemies that might be using Darkrai's power for evil.
Haku should definitely be included. Since Haku was Zabuza's loyal follower, his presence can add depth to the story. He could act as a mediator between Naruto and Zabuza at times. Also, Kakashi can be a great addition. His history with Zabuza makes for an interesting dynamic, and his mentoring of Naruto can play a role in how Naruto interacts with Zabuza.
Well, in addition to Naruto and Urahara, Ichigo from Bleach could be a great addition. Since Urahara has a connection with Ichigo, and Naruto's energetic and positive nature could create an interesting dynamic with Ichigo's more brooding personality.
Definitely Naruto himself. His determination and positive attitude can bring a lot to the story. Lala too, of course, with her fun - loving and inventive nature. Sakura could also be a great addition. She could interact with Lala in interesting ways, perhaps learning about Lala's technology and applying some of her medical skills to help Lala if she gets injured.
Madara Uchiha would be an excellent character to include. His long - standing relationship with Hashirama, filled with both friendship and enmity, and his connection to Sasuke and the overall ninja world's history would make for a very engaging fanfiction.
Naruto himself is a must - he's the main character after all. Sasuke could also be great as his rival. Their interactions around the kit would be interesting, like if they both wanted it for different reasons. Sakura could be included too, maybe she helps Naruto figure out how to use the kit.
Definitely Sasuke. His complex relationship with Naruto provides a lot of material for fanfiction. You can explore their friendship, rivalry, and how they grow together. Kakashi is also a great character to include. His wisdom and unique jutsu can add depth to the story. And of course, Sakura. Her growth as a kunoichi and her relationships with Naruto and Sasuke can be interesting to write about.
Definitely Naruto himself. His unique abilities and his never - give - up attitude would add a lot to the story. For Salem's side, Salem herself is a must - include as she is the central figure in her world. Also, characters like Sasuke from Naruto could be interesting as his complex personality and powerful skills would create interesting dynamics. And maybe some of Salem's loyal followers like Cinder could also be included to add more conflict.