What could be an interesting plot in a 'Ben 10 and One Piece crossover fanfiction'?

It could be about Ben using his alien forms to fight alongside the Straw Hat Pirates in the One Piece world. Maybe he uses Heatblast to help Luffy against a fire - based enemy on a new island they discover.

One possible plot could be Itachi arriving in the One Piece world and being mistaken for a powerful new pirate. The Straw Hats might initially be cautious but then realize his skills could be useful. Itachi, with his Sharingan, could help them in battles against the World Government or other strong enemies. For example, his genjutsu could be used to deceive opponents during sea battles.

One idea could be that the Straw Hats end up in the Naruto world. Luffy might befriend Naruto and they could team up to fight a common enemy like Akatsuki members who are after some powerful Devil Fruits that have mysteriously appeared in the Naruto world. Zoro could have duels with some of the skilled sword - users in the Naruto universe, like Sasuke or Killer Bee when he uses his sword - like Samehada.

Perhaps there's a powerful and mysterious treasure in the RWBY world that the Straw Hats hear about. It could be something related to the Dust or an ancient relic. They team up with the RWBY characters to search for it. Along the way, they encounter various villains from both universes who also want the treasure. Ruby's speed and Crescent Rose could be compared to Usopp's long - range attacks, and Blake's stealth could be useful in sneaking past enemies. The story could explore how the different powers and personalities interact during this adventure.

One possible plot could be that the Straw Hat crew sails to the world of Sekirei. Luffy might be intrigued by the concept of Sekirei battles and try to participate in a friendly way. Maybe Zoro would find some Sekirei with interesting sword - fighting skills and have duels with them. And Nami could be interested in the economic aspects of the Sekirei world, like how they trade resources or manage their finances.

In a crossover fanfiction, it could be that the power of Devil Fruits from One Piece becomes known in the Dragonball universe. Vegeta, being his prideful self, wants to obtain a Devil Fruit power to make himself even stronger. He travels to the One Piece world and accidentally ends up on the Thousand Sunny. The Straw Hat crew initially see him as a threat but then realize they can help each other. They end up in a big adventure together where they combine their powers to fight a new common enemy that threatens both universes.

Here's another plot. There's a new villain in the One Piece world who uses lemon - based weapons and has a vendetta against the minks. Carrot gets targeted. The villain's weapons are made from super - acidic lemons that can corrode ships and even harm the toughest of pirates. The Straw Hat crew, with Carrot on board, has to figure out the weakness of these lemon weapons and defeat the villain before he causes too much destruction.

Maybe Naruto, in his godlike state, is mistaken for a powerful devil fruit user in the One Piece world. The Straw Hat crew initially views him with suspicion but then realizes his good intentions. He could teach the crew some of his ninja techniques, like shadow clones, which could be used in creative ways during battles or to perform tasks on the ship. The story could also involve Naruto's search for a way back to his own world while getting involved in the various adventures and conflicts in One Piece.

A cool plot could be that the Highschool DxD characters are transported to the One Piece world. Issei, being the perverted yet brave character he is, might be really excited to see all the different female characters in One Piece. But he also realizes that they are in a dangerous world. Meanwhile, the One Piece characters are baffled by the strange powers and personalities of the Highschool DxD crew. They all have to work together to face the various pirates and threats in the One Piece world.

Another plot could be that an evil force in the RWBY universe discovers the existence of the Omnitrix from another dimension. They manage to create a device to pull Ben and the Omnitrix into their world. Ben has to adapt quickly to this new world while Team RWBY, who are initially suspicious of him, realizes that he could be an ally against this new threat. They join forces, with Ben using his alien forms in creative ways to combat the Grimm and the evil force's minions.