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.
One common theme is the clash of combat styles. For example, when Zoro crosses over to a world like Naruto's, his swordsmanship clashes with ninjutsu. Another theme is adaptation. Zoro has to adapt to new environments, like if he's in a world with different magic systems or cultures.
Blackbeard would probably be very interested in the magic in the Fairy Tail world. He might try to steal some of the powerful magic items or learn magic for himself. He could see the mages as a threat to his plans if they oppose him, but also as potential allies if he can manipulate them. He would likely use his cunning and power - hungry nature to his advantage in this new world.
Maybe there could be a situation where the Devil Fruits in One Piece are related to the Hollow powers in Bleach. Some of the characters in One Piece start showing Hollow - like traits due to a strange phenomenon. Zoro, for instance, might start having an inner struggle similar to how Ichigo battles his inner Hollow. And the Bleach characters have to help the One Piece crew figure out what's going on and how to control these new powers.
Aokiji is popular too. His more laid - back approach to justice compared to Akainu makes him a great character for crossovers. He can form interesting relationships with other characters, and his ice - based powers can be used in creative ways in different crossover scenarios.
Well, the character development is a big part. In these crossovers, admirals might find themselves in situations that force them to change their views. Like if they are paired with a more morally gray character from another part of the One Piece world. They could start to question their strict sense of justice. This adds a whole new layer to their personalities.
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.
One interesting aspect is the character interactions. Characters like Goku and Luffy, who have such different personalities but similar heroic traits, coming together. Goku's pure - hearted love for fighting and Luffy's determination to protect his crew can lead to some great dialogue and storylines. Also, the different settings of the two series being merged. The vast ocean - based world of One Piece and the various planets in Dragon Ball Z create a whole new backdrop for the crossover fanfiction.
If Naruto met Newgate in a fanfiction, Naruto would likely try to understand Newgate's world view. Naruto is all about protecting his friends and village, while Newgate has his own code among the pirates. They could end up having a philosophical discussion about power, loyalty, and the meaning of family. Naruto might learn about the complex relationships in the pirate world, and Newgate could be intrigued by Naruto's ninja skills.