It could be amazing. Maybe Luffy and his crew end up in the Avatar world. Luffy might be intrigued by the bending powers and try to learn them in his own goofy way. Zoro could have a sword - fighting duel with some of the best benders. And Nami would probably be interested in the unique treasures and cultures of the Avatar world.
In a One Piece x Korra crossover, the story could center around a common enemy. For example, a powerful dark force that is threatening both the One Piece world and the Avatar world. Korra and Luffy would team up. Luffy's fearless leadership and Korra's determination would make them a great duo. The other characters from both universes would contribute their unique abilities. Sanji could cook special dishes for Korra and the Avatar team, while Tenzin could teach some airbending principles to the Straw Hats who are interested.
The plot could involve a villain from One Piece using the power of bending against the world of Korra. For example, Blackbeard discovers a way to steal bending abilities and starts causing chaos. Korra, in her quest to stop him, meets the One Piece crew who are also affected by Blackbeard's actions. Together, they combine their skills, with Korra's bending and the Straw Hats' various fighting styles and Devil Fruit powers to take on Blackbeard.
It could be Brook. A skeleton in the Avatar world? He'd be a total anomaly. His music might have strange effects on the bending elements. He could also tell the Avatar characters stories about his past life and his adventures with the Straw Hats. The Avatar characters would be both fascinated and a little creeped out by him.
Zoro's swordsmanship could interact well with earthbending. Earthbenders could create structures for Zoro to jump off of and gain more momentum for his attacks. His three - sword style could be adapted to work with the flow of earth or water if he were to fight alongside benders. As for Sanji, his kicks could be combined with firebending techniques. He could use the heat generated by a firebender to increase the power of his Diable Jambe kicks. And the Straw Hats' Haki could also play a role, perhaps being able to sense the presence of benders or even disrupt their bending abilities in some cases.
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.
Well, a Goku - One Piece crossover fanfiction might involve Goku getting lost in the One Piece universe. He could end up on a random island and befriend Luffy and his crew. Goku would probably be interested in the different Devil Fruits and might even try to use his powers to help them find the One Piece. His fighting skills would also be a great asset during battles against the likes of the Yonko or the World Government's forces.
A Legend of Korra and Star Wars crossover would likely have some really cool character interactions. Aang's spirit could meet Yoda's. They could share their wisdom about the balance of the universe. Also, the technology from Star Wars like lightsabers and starships would be fascinating to see in the world of Legend of Korra. How would the people of that world react to such advanced technology? It could lead to some great storylines about adaptation and progress.
It could be really exciting. Imagine Luffy meeting Superman. Luffy's rubber powers against Superman's super strength would be a sight to see. Maybe they'd start off as rivals, not understanding each other's ways at first, but then realize they both fight for justice in their own worlds.
One possible plot could be that the Straw Hat Pirates end up in the Fairy Tail world due to some magical anomaly. They team up with the Fairy Tail guild to fight a common enemy like a powerful dark wizard who has the power to control the seas as well. Luffy and Natsu could have a friendly competition about who is stronger while their respective crews and guild members learn from each other's fighting styles.
Well, it could be about the Straw Hats accidentally ending up in the Marvel universe. They meet the Avengers and at first there's some misunderstanding because of their different ways. But then they realize they can work together. Maybe Luffy is fascinated by Thor's hammer and tries to lift it, while Zoro wants to have a sword fight with Captain America's shield.
Well, in a One Piece and Dragonball Z crossover fanfiction, the art styles are quite different, but that could add to the charm. For example, the colorful and outlandish characters from One Piece would contrast with the more muscular and intense look of Dragonball Z characters. Maybe the Straw Hat crew would be intrigued by the Dragon Balls and their power to grant wishes. They could embark on a journey to find all the Dragon Balls, while also dealing with the likes of Cell or Majin Buu who are interested in their unique abilities.