Well, they might become friends. Goku, being the kind - hearted boy he is, would probably be curious about Android 18. Maybe they'd start training together, with Goku showing Android 18 some of his martial arts moves. And Android 18 could show Goku some of her advanced technology - like knowledge, if she had any in her android form even as a kid. They could also get into all sorts of adventures, exploring the world around them and getting into harmless little troubles.
Well, at first they might be a bit wary of each other. But as time passed, they'd discover their common interests like the pursuit of strength. Goku's positive attitude would influence Android 18, and she would in turn help Goku with things like problem - solving from her android - smart perspective. As they grew older in the fanfiction, this relationship could become a very deep and important one, with them having each other's backs no matter what.
Honestly, comparing the strength of anime Goku and manga Goku is tricky. Both versions have their unique strengths and challenges depicted differently, making it hard to make a clear-cut comparison.
One possible adventure is that they explore an uncharted planet. Since they are kids, they would be full of curiosity. On this new planet, they might discover strange creatures and new power - ups. The Saiyan girl could use her intelligence to figure out how to deal with the new environment, while Goku uses his brute strength when they face any threats.
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.
Another possible main character could be the villain that forces the two Gokus to meet. This villain could be a new, super - powerful threat that the two Gokus need to deal with. Their meeting becomes a crucial part of the story to defeat this powerful foe.
One of the characters who could betray Goku is Piccolo. Although they've been allies for a long time, in fanfiction, things can change. Perhaps an ancient evil force takes control of Piccolo's mind and makes him turn on Goku. Or it could be Krillin. He might be influenced by an outside force that convinces him Goku is becoming too dangerous. Also, don't forget about the Kais. If there's some sort of power imbalance or a threat they perceive from Goku, they might betray him to maintain the order of the universe in the fanfiction.