Maybe a story where Bulma uses her scientific genius to help Batman upgrade his gadgets. She could be intrigued by his technology and offer her own unique insights. In return, Batman could teach her some of his detective skills, which she could use to help Goku and the others solve some mysteries on their own planet. And this could lead to an alliance between the Z - fighters and the Justice League.
One idea could be a battle between Goku and Superman. They could start off as rivals, each thinking their own planet needs more protection. As they fight, they gradually realize they have more in common than they thought, like their strong sense of justice. Then they team up to face a common enemy, like Darkseid and Frieza working together.
A cool concept would be if the Dragon Balls were brought into the DC universe. The heroes and villains of DC would be scrambling to get them. Superman might be interested in using them for good, while Lex Luthor would want them for world domination. Meanwhile, Goku and his friends are trying to protect the Dragon Balls from falling into the wrong hands in this strange new universe.
Maybe a story where the Dragon Balls are accidentally sent to the DC universe. This would attract the attention of characters like Batman who would be intrigued by their power. Then, characters from Dragon Ball would have to travel there to retrieve them, leading to all sorts of encounters and battles.
One idea could be a crossover with the Naruto universe. Imagine Goku meeting Naruto and them having a friendly sparring match. Another could be a crossover with the One Piece world, where the Z - fighters team up with the Straw Hat Pirates to take on a common enemy. And a crossover with the Harry Potter universe, with the Saiyans learning magic at Hogwarts.
A great 'Dragon Ball Super Crossover Fanfiction' concept might involve a crossover with the Harry Potter world. The Saiyans could visit Hogwarts. Maybe Vegeta could be really intrigued by the magic there and try to learn some spells, while at the same time the wizards are in awe of the Saiyans' power. There could be a dark wizard who wants to use the Dragon Balls for his own evil purposes, and the Hogwarts students and the Z - fighters have to work together to stop him.
A crossover with the One Piece universe could also be cool. Imagine Luffy and Goku having a friendly competition to see who can defeat more enemies. The different power systems, like Devil Fruits and ki, would create interesting battles and interactions.
One idea could be that Goku and Naruto meet in a strange dimension. They initially mistake each other for an enemy but then realize they have a common goal, like saving both their worlds from a new powerful villain. Goku could teach Naruto some of his ki control techniques, and Naruto could show Goku some of his more unique jutsu.
One idea could be that Goku and his friends are on a quest to find the rarest Pokemon in the Dragon Ball Z world. Maybe the Dragon Balls have the power to summon legendary Pokemon. For example, the Saiyans could use their fighting skills to train Pokemon for battle. Another idea is that the villains from Dragon Ball Z, like Frieza, try to capture powerful Pokemon to use in their evil plans.
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.
A possible plot for the crossover fanfiction could be that Ruby discovers a way to travel to the Dragon Ball universe. There, she meets Goku and the others and learns about ki and the different power - ups. She then brings this knowledge back to Remnant and tries to teach her friends. At the same time, some of the Dragon Ball characters could be curious about Remnant and follow Ruby back. This leads to a series of adventures where they have to deal with both the Grimm and the power struggles in Remnant, all while trying to understand each other's worlds better.
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 idea could be that the Soul Reapers from Bleach team up with the Z - Fighters from Dragon Ball Z to fight a common powerful enemy. For example, a new type of demon that has the ability to absorb spiritual energy like in Bleach and also has the strength and fighting skills similar to the villains in Dragon Ball Z.