Sure. There could be fanfiction on this. Goku is a well - known character for his strength and determination. Android 21, on the other hand, has her own allure. Writers might find it interesting to pair them up romantically. It could involve Goku helping Android 21 understand more about humanity and love, or perhaps Android 21 being drawn to Goku's unwavering spirit in a way that develops into love.
Unique storylines. For example, a story where Android Goku has to face an entirely new kind of threat that the regular Goku never had to deal with. It could be a technological virus that affects his android parts in a strange way.
A possible plot could be that Android 18 and Goku are thrown into an alternate dimension where they have to rely on each other to survive. In this dimension, they face challenges that test their friendship and fighting skills. Android 18 might learn some of Goku's signature moves and Goku could learn more about the technology within Android 18.
Their relationship could develop into a deep friendship. Goku, being the kind - hearted fighter he is, would likely accept Android 18 for who she is. And Android 18, seeing Goku's strength and good nature, would start to respect him more and more.
Common themes often involve the unexpectedness of their relationship. Since Goku is a pure - hearted warrior and Android 18 was initially an enemy. In lemon fanfictions, there might be a focus on the passion that arises from this unusual pairing. Also, themes related to redemption and acceptance can be found, as Android 18 might find acceptance in Goku's world, and Goku might see her in a new light. This all gets intertwined with the more 'lemon' aspects which are often used to heighten the intensity of their relationship.
Often, it could be new villains created specifically for the fanfiction. Maybe a powerful android created by the same scientist who made Android 21 but with a more evil intent.
In some fanfics, other characters might also play a role. For example, Krillin, who was once in a relationship with Android 18. His presence could add an interesting dynamic, like jealousy or a sense of competition, to the relationship between Goku and Android 18.
A fanfiction about them in love might show Goku teaching Android 21 about the joys of food, since he loves to eat. Android 21, who may have a different view on sustenance as an android, could start to appreciate the concept of enjoying a meal through Goku's influence. In terms of their relationship, there could be moments of confusion as Goku tries to understand his new - found feelings for an android, and Android 21 struggles with her own emotions which are a new experience for her. Their love story could be filled with these kinds of unique and endearing interactions.
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.