Sasuke would be a great addition. His skills and his complex relationship with Naruto could add a lot of depth to the story. He could have some interesting interactions with the Second Mizukage, perhaps learning from him as well. Another good character would be Sakura. Her medical ninjutsu could come in handy in various situations in the story, and she could also provide a different perspective compared to Naruto and the Second Mizukage.
Gaara would also be a good choice. His own journey of redemption and his sand - based powers could create some unique interactions. He could form an unlikely alliance with the Second Mizukage, and together with Naruto, they could face a common enemy that threatens all of their villages. This would bring out different aspects of their personalities and powers.
Kakashi is also a popular character. He might be sent as an emissary from the Hidden Leaf to the Hidden Mist, and his experience and knowledge play a crucial role in diplomatic or ninja - related matters in the fanfiction. His Copy Ninja skills are always a draw.
Sasuke could also be a great pairing. Given his past and his complex nature, his interactions with the Godaime Mizukage could be full of tension and intrigue. He might have his own motives when dealing with the Hidden Mist, and she would have to be cautious around him. They could also end up having to fight side by side against a common enemy, which would be really cool.
Another character could be Kakashi. Kakashi's wisdom combined with Byakuya's combat skills and Naruto's determination would make for a really engaging story. Kakashi could study Byakuya's techniques and try to incorporate some of that into Naruto's training, while also trying to understand Byakuya's motives in the Naruto world.
I think Mario and Hinata would be an interesting pair. Hinata's shy but strong - willed nature could contrast with Mario's always - positive and heroic attitude. And Mario could help Hinata become more confident in this cross - over scenario. Another good pair could be Toad and Shikamaru. Toad's small but brave self and Shikamaru's intelligence would make for an engaging dynamic.
Sasuke could be a great addition. His complex relationship with Naruto already exists and adding Touka to the mix could create some really interesting dynamics. They could all be involved in a high - stakes battle against a new and powerful enemy.
Sasuke could also be an interesting character to pair with Gohan. Sasuke's brooding nature and his quest for power could contrast with Gohan's more altruistic motives. They could have some intense battles and then later come to understand each other better. Maybe Gohan could help Sasuke see a different path than his revenge - driven one.
Naruto himself could be a great character to pair with Magneto. Their different powers and personalities would create an interesting dynamic. Naruto's positive and determined attitude could contrast with Magneto's more serious and sometimes harsh nature. Also, they could learn from each other's combat styles and strategies.
Well, Hinata could be paired with Guren in some fanfiction. Hinata's shy yet strong - willed nature could contrast with Guren's more assertive personality. It could lead to stories about friendship or even a mentorship kind of relationship. Kiba and his dog Akamaru could also be paired with Guren. Their teamwork - based fighting style could add a new dimension to stories involving Guren in the Naruto fanfiction world.
Naruto and Jack would be a great pair. Naruto's energetic and never - give - up attitude would mesh well with Jack's determination in Kickin It. They could learn a lot from each other, like Naruto teaching Jack about chakra control and Jack teaching Naruto some advanced martial arts moves.
Another good pair could be Kakashi and Eminem. Kakashi is a very laid - back yet highly skilled character. His calm demeanor could contrast well with Eminem's energetic and often angry - inspired lyrics, leading to some unique exchanges and perhaps even Kakashi learning a thing or two from Eminem about expressing emotions.