One possible plot could be that Luffy and his crew are sailing in the Grand Line when they encounter a strange energy. It turns out to be a Dragon Ball. They then have to deal with various villains from both universes trying to get the ball. Maybe Frieza hears about it and teams up with some of the pirates from One Piece. And Goku, sensing the power of the Dragon Ball, also arrives in the One Piece world to help Luffy protect it.
A cool plot could be that the Dragon Balls are scattered across the One Piece world. Goku and his friends lose their memories and end up in different parts of the world. Luffy and his crew find Goku and try to help him regain his memory. As they search for the Dragon Balls, they encounter all sorts of enemies. Some of the One Piece villains like Doflamingo try to use the Dragon Balls for their own desires. And the Saiyans start to remember their powers slowly as they fight alongside the Straw Hats.
One possible plot could be that Goku and his friends somehow end up in the One Piece world. They meet Luffy and his crew. Goku might be interested in the Devil Fruits and their powers. Luffy, on the other hand, would be excited to see Goku's super strength and ki abilities. They could team up to fight a common enemy like a powerful pirate who has also acquired some sort of dragon ball - like artifacts. This would lead to an epic adventure with both the Saiyans' and the Straw Hats' unique fighting styles combined.
In a crossover fanfiction, the Dragon Balls could be the key element. Suppose the One Piece characters learn about the Dragon Balls and their ability to grant wishes. Luffy would definitely want to use them to make some crazy wishes, like having an unlimited supply of meat. However, the villains from both universes also get wind of this. Frieza could team up with some of the powerful pirates like Blackbeard. This would force the heroes of both worlds to join forces. Goku and Luffy would lead their respective teams in a battle against this new, powerful alliance, with the fate of both universes at stake.
Well, it could be about Goku ending up in the One Piece world. Maybe he teams up with Luffy to fight a common enemy. For example, a powerful pirate who has some sort of dragon - like powers similar to the dragons in Dragon Ball. They would combine their unique fighting styles. Goku's energy blasts and Luffy's stretchy attacks would make for an epic showdown against the bad guy.
In a 'Harry and Dragon Ball' crossover fanfiction, perhaps the Deathly Hallows and the Dragon Balls have some sort of hidden connection. Harry, Ron, and Hermione are on a quest to find out more about this connection when they are suddenly whisked away to the Dragon Ball universe. There, they meet Bulma who is intrigued by their magic. Harry's scar starts acting up in a new way, as if it's reacting to the powerful ki in this universe. They soon learn that a new, powerful dark force is emerging that is related to both Voldemort and some of the Dragon Ball villains. They must combine their magic and the power of the Dragon Balls to stop this new threat.
Well, perhaps the Saiyans in Dragon Ball Z detect the strong energy from the Devil Fruits in One Piece. Vegeta decides to visit the One Piece world to see if he can gain an edge over Goku. Meanwhile, the Straw Hats are dealing with a new threat that seems to be more powerful than any they've faced before. Vegeta initially clashes with the Straw Hats but then realizes they need to work together. They combine their skills, like Goku's Kamehameha and Luffy's Gear Fourth, to take on the big bad.
One idea could be a crossover with the Naruto universe. Goku and Naruto could team up to fight a common enemy. Maybe they face an evil villain who has the power - stealing abilities like Cell and the ability to use powerful ninja jutsus. Another plot could be a crossover with One Piece, where Luffy and Goku have a friendly competition about who can eat more food and then end up having to work together to defeat a new threat at sea that has the strength of Saiyans and the deviousness of pirates.
Well, a cool plot for Dragon Ball Xenoverse Crossover Fanfiction could be a time - traveling crossover. Imagine characters from different anime universes being brought to the Dragon Ball Xenoverse timeline. For example, characters from Fullmetal Alchemist arrive in the Xenoverse. Edward could use his alchemy skills against the Dragon Ball villains, and Alphonse could have some really interesting interactions with the Dragon Ball characters, like Bulma or Master Roshi.
A cool plot could be a tournament - style crossover. A powerful being from another dimension decides to host a tournament where fighters from Dragon Ball Z and Devilman are invited. Characters like Vegeta and Devilman's friend Akira Fudo would compete. There could be unexpected alliances and rivalries. For example, Piccolo might initially see Devilman as a threat but later realize they have a common goal of protecting their respective worlds. And in the end, they all have to team up against the true evil that the tournament organizer has in store.
One idea could be that Broly is transported to an alternate universe where he teams up with Goku from a different timeline to fight a new, powerful enemy. They have to combine their unique fighting styles to stand a chance.
One possible plot could be that the characters from Awog end up in the Dragon Ball universe. They might initially be confused by the high - power levels and strange creatures. The Saiyans could mistake them for new threats or allies. For example, Goku might offer to train them in his martial arts style, leading to some comical and action - packed training sessions as the Awog characters try to keep up with Goku's intense regime.