One idea could be that Naruto gains the powers of Captain Planet. He could use the power of Earth to create new jutsu related to the ground, like summoning huge boulders in a more eco - friendly way. Another could be a crossover where the villains in Naruto's world are causing environmental damage, and Captain Planet and his team come to help Naruto and his friends stop them. They'd combine their skills, with Naruto's ninja techniques and Captain Planet's elemental powers.
A cool fanfiction concept could be that the characters from Naruto are reincarnated in the world of Captain Planet. They have to adapt to this new world with its different rules and powers. Sasuke could be interested in the power of fire in Captain Planet's world and try to master it in his own way. Sakura might focus on the power of heart and use her medical skills to help heal the planet. Naruto, of course, would be at the center, trying to bring everyone together to protect the new world like he did in his own.
One interesting idea could be the fusion of Naruto's ninja world with the Planet Hulk concept. Maybe Naruto characters having to deal with the harsh environment of Planet Hulk. For example, Sasuke might find new and powerful opponents there that force him to adapt his Sharingan abilities in unique ways.
There could be a fanfiction where the Captain Planet characters travel to different planets to learn about their environmental conservation methods. For example, they visit a planet where the inhabitants have a unique way of recycling energy that the Planeteers could bring back to Earth to help solve their own energy problems. This would involve a lot of adventure and discovery as they interact with alien species.
You could write about a group of Naruto characters traveling to a mysterious 'planet naruto fanfic' and having to adapt to its strange environment. They might encounter new enemies and form unexpected alliances with the locals there.
One interesting plot idea could be Captain Amelia getting stranded on a strange planet with only her wits and a few basic supplies. She has to navigate the unknown terrain, deal with alien creatures, and find a way to repair her ship and get back to her crew. Another could be a pre - Treasure Planet story, showing how she became the fearless captain she is, perhaps facing discrimination in a male - dominated space - faring world and fighting her way to the top. A third idea might be a story where she teams up with an unlikely ally, like a young stowaway, to stop a space pirate threat to the galaxy.
Another idea is that there's a villain who can manipulate time and space. He sends Captain America to the Naruto world during a crucial time in Naruto's story, like right before a big battle. Captain America's leadership and battle experience help Naruto and his friends come up with a better strategy. And in the process, they learn from each other's values and fighting styles.
One idea could be a crossover where the Naruto characters interact with the Shinigami captains in a battle against a common enemy. For example, Naruto's unique jutsu combined with a Shinigami captain's zanpakuto abilities would make for some epic fight scenes.
One idea could be a crossover where Naruto characters end up on the Cat Planet. They could learn about the unique cat - like cultures and powers there. Maybe Naruto tries to teach the cat people his ninja way, while also learning their feline - based fighting styles.
One idea could be that Naruto and Captain Marvel are brought together by a powerful cosmic force. They have to combine their unique abilities, Naruto's ninja skills and Captain Marvel's superpowers, to defeat a common enemy that threatens both their worlds. For example, a powerful alien race that is draining chakra from Naruto's world and energy from Captain Marvel's universe.
One plot idea could be that Naruto and Captain Samui team up on a special mission. Maybe they have to infiltrate an enemy base. Samui's strategic skills combined with Naruto's power would make for an exciting adventure.
There might be a fanfic where the focus is on a different kind of 'power' that comes from their gay relationship. Maybe their love gives them an extra boost in their fight against pollution and evil forces. It could also delve into how they discover and accept their feelings in a world that might not be entirely accepting at first.