Well, in a Goku and Marvel crossover fanfiction, the story could start with Goku somehow ending up in the Marvel universe. He might initially be confused but quickly adapt. He could get involved in the conflicts of the Marvel world, such as the ongoing battles between the X - Men and the Brotherhood of Mutants. His pure - hearted nature might influence some of the more morally ambiguous characters in Marvel. And his training - obsessed attitude could inspire characters like Spider - Man to train harder and reach new levels of power.
The characters could interact in many ways. Goku could have a friendly sparring match with Captain America. Cap would be impressed by Goku's power and fighting skills, and Goku would respect Cap's leadership and unwavering will. Or Goku could help Iron Man upgrade his suit with some of his Saiyan technology knowledge.
I think in 'Marvel The Flash Crossover Fanfiction', the most interesting part would be how the Flash's abilities are perceived in the Marvel universe. Since the power scales and the overall feel of the two universes are different. Maybe the Flash would be seen as an anomaly, or perhaps a new kind of hero that the Marvel characters have to adapt to. It could also explore how the Flash's speed affects time and space in a world that already has characters like Doctor Strange who are well - versed in such concepts.
Trunks is another good option. His time - traveling experience and sword - fighting skills could add a new dimension to the crossover. He and Xeno Goku could work together to prevent disasters in different timelines.
In a Goku Naruto crossover, both characters have their own strengths. Goku's physical strength and energy attacks are off the charts. His ability to instantly teleport and sense ki gives him an advantage in combat. Naruto, though, has a unique power system. His connection to the Nine - Tails and his ability to use different types of chakra make him a force to be reckoned with. If we consider a battle, Goku's power might seem greater on the surface. But Naruto has the advantage of being able to surprise his opponents with his ninjutsu and clones. Also, Naruto has a strong willpower that has allowed him to overcome many tough situations, which could play a role in a fight against Goku.
Goku might teach Naruto about the concept of Super Saiyan forms. Although Naruto doesn't have Saiyan blood, he could learn about the idea of unlocking different power levels through intense emotions and training. For example, Naruto could find a way to apply the idea of Super Saiyan rage - like power - ups when he's in a really tough battle and needs that extra boost.
A Goku crossover with the Pokémon world could be really fun. Goku could try to catch Pokémon using his speed and strength. He might also team up with Ash to battle powerful Pokémon trainers. Or how about a crossover with the Digimon world? Goku could enter the Digital World and help the Digimon in their battles against evil Digimon using his energy attacks.
One common theme is power struggles. Since Black Goku is a very powerful character, when he crosses over, there are often battles to determine who is the strongest in the new combined universe.
Another option is a crossover with a different anime world, like Naruto. GT Goku could end up in the Hidden Leaf Village. The shinobi would be amazed by his power. Goku, being Goku, would be interested in learning their ninja techniques. They could team up against a common enemy that somehow has the ability to use both chakra and ki, creating a unique and exciting battle scenario.
Well, one unique aspect is the combination of different power scales. For example, when Goku crosses with a character from a less powerful universe, it shows how his god - like powers can completely disrupt the balance. It's like a fish out of water situation but in a power - level sense.