Another possible storyline is that Android 21, who is usually seen as a bit of an outcast, finds acceptance in Goku's group. Goku encourages the others to give her a chance. They then go on adventures together, with Android 21 constantly evolving not just in power but also in her understanding of the world around her.
One interesting storyline could be Goku and Android 18 teaming up to fight a new, powerful enemy that neither of them can defeat alone. They have to learn to combine their skills and powers in unique ways.
Another storyline could be a time - travel one. Android 21 somehow gets sent back in time and meets a younger Goku. This would be really interesting as she would have knowledge of future events and technologies. Goku, being his curious self, would be intrigued by her and want to learn from her. They could team up to prevent some of the future disasters that Android 21 knows about.
One idea could be that Goku and Android 21 team up to face a new and extremely powerful villain. This villain could be from another dimension and has the power to corrupt the minds of other fighters. Goku, with his pure heart and Android 21's intelligence, find a way to defeat the villain.
In some fanfictions, a possible plot is that Android 21 discovers a way to transfer some of Goku Black's power into herself, creating a new form for her. This form has a mix of her android features and Goku Black's dark energy, leading to a whole new set of adventures as she tries to control this power.
One interesting story could be about Goku and Android 18 teaming up for a special tournament. In this fanfiction, they put aside their differences and combine their powers to face a new and powerful enemy. Goku's Saiyan strength and Android 18's unique android abilities make them a formidable duo.
Maybe in a post - battle scenario, Goku and Android 18 are left alone to recover. They begin to have conversations about their different origins. Goku shares about his Saiyan heritage and training, while Android 18 talks about her creation by Dr. Gero. This exchange could lead to a deeper emotional connection between them.
One interesting storyline could be about Naruto having a different power origin. For example, instead of being the host of the Nine - Tails, he might gain his power from an ancient sage. This could change the whole dynamic of his character development and relationships in the story.
There is a fanfic called 'Beyond the Battlefield'. In this story, Goku and Android 18 are forced to team up for a mission. As they work together, they start to understand each other better. The author does a great job of writing their dialogues, which are full of humor and some underlying tension.
One popular Goku x Android 18 fanfic could be 'A New Bond'. In this fic, it might explore how Goku and Android 18, who are from different origins, start to develop a unique relationship. It could show their interactions and how they gradually understand each other on a deeper level.
One possible storyline could be them teaming up for a tournament. Gohan's martial arts skills combined with 18's strength would make for an interesting duo in the fighting arena. They could face various opponents and learn to trust each other's abilities more.