In some versions, the female Goku could be part of a prophecy. The two Gokus meet, and at first, there is some confusion and misunderstanding. But as they get to know each other, they discover that they are key to fulfilling the prophecy. They combine their powers and defeat an ancient evil that was threatening both of their worlds.
Maybe Gine meets Goku during a time when he is facing a great internal struggle. She offers him the motherly love and guidance he never had growing up. This could lead to Goku having a new sense of purpose and inner peace, which in turn affects his relationships with his friends and family on Earth.
Maybe in the fanfiction, Goku helps Videl discover a new power within herself. He trains her in his special way, and she becomes much stronger as a result. It could also involve some comical moments where Goku's naivete about normal life clashes with Videl's more down - to - earth personality.
In some 'Goku meets Goku fanfiction', they could team up against a super powerful enemy that neither could defeat alone. They would combine their signature moves like the Kamehameha for an ultimate attack.
One idea could be that Goku and Goku Black are forced to team up against an even greater threat from another universe. They start to understand each other's fighting styles during the battle and gradually develop a grudging respect for one another.
One interesting idea could be the clash of their different power systems. Goku has his ki-based attacks and Super Saiyan forms, while Sonic has his speed and Chaos Emerald powers. Maybe they could have a friendly sparring match to test each other's abilities.
One idea could be that Goku accidentally travels to the RWBY universe during a sparring session that goes wrong with Whis. He could be mistaken for a powerful Grimm at first, causing chaos. Then, he teams up with Team RWBY to fight a new super - strong Grimm that threatens all of Remnant.
A plot could involve a love triangle where Female Frieza has feelings for Goku, but Goku is oblivious and focused on his own goals. Meanwhile, another character is also interested in Goku. This could lead to a lot of comical and tense situations. Or perhaps Female Frieza challenges Goku to a series of contests not related to fighting, like cooking or dancing, to prove she can be better than him in other areas.
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.
One idea could be a crossover universe where Goku somehow ends up in the Naruto world and meets Sakura. They could team up to fight a new common enemy that is causing chaos in both their worlds. Maybe this enemy has the ability to steal energy like the Saiyans but also uses genjutsu like the ninjas.
One plot idea could be that Baby takes over Goku's body and tries to use his power to conquer the universe in a more subtle way. He might pretend to be Goku at first and manipulate his friends into doing his bidding without realizing it.