In the fanfiction, their relationship could be one of mutual admiration. Kid Goku would look up to Future Goku for his experience and power. Future Goku, on the other hand, would be charmed by Kid Goku's innocence and raw potential. They could train together, and during this process, they would form a strong brother - like relationship.
In a fanfiction where Kid Goku meets Future Goku, one possibility is that Future Goku would be amazed at seeing his younger self. He might share some of the dark experiences he has had in the future, like the battles against powerful enemies and the losses. Kid Goku, being young and full of energy, could be inspired by Future Goku's strength and determination. Maybe he would start training even harder, eager to reach the level of his future self.
In a fanfiction where Future Gohan meets Goku, it could be an emotional reunion. Gohan might be filled with a sense of relief and joy, seeing his father again. He could show Goku all the things he's been through in the future, and Goku would be both proud and sad about what his son has endured.
It could lead to some really interesting plot twists. Maybe Goku could prevent major disasters before they happen and change the course of events in the Dragon Ball universe.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
Well, they might be shocked at how much technology has advanced in the future depicted in the fanfiction. Maybe there are new types of elemental powers or different ways of training ninjas. It could also be that the relationships between characters have changed in unexpected ways, and they would have to come to terms with that.
In the fanfiction, perhaps they team up to fight a common enemy. Goku's raw power combined with Gohan's strategic mind from the future battles could make them an unbeatable duo. They'd exchange blows and strategies, and their teamwork would be amazing to read about.