Chi - Chi might be one of the first to support them. Despite her past relationship with Goku, she could see how happy Goku is with Android 18 and decides to be happy for them. Also, Krillin would likely support the marriage. He has a deep friendship with both Goku and Android 18. He knows Android 18 well and trusts Goku, so he would be all for their union.
One possibility could be a story where Android 21, with her unique powers and intelligence, teams up with Goku to face a new and powerful enemy. Maybe they start off as reluctant allies, with Goku being a bit wary of Android 21's past as an android. But as they fight together, they learn to trust each other and their combined strength becomes a force to be reckoned with.
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.
A possible plot could be that Android 18 gets injured during a fight and Goku takes it upon himself to protect and heal her. This close proximity leads to the development of feelings, which is where the 'lemon' part might come in. Their relationship could be a secret at first as they are from different 'worlds' in a sense, with Goku being a Saiyan hero and Android 18 being an android once created for destruction.
One possible scenario in this fanfiction could be that Android 18 and Goku are forced to time travel due to a new threat that endangers the entire universe. They might travel to a time when the Saiyans first arrived on Earth. Goku, with his knowledge of the future, could try to change some events to prevent future disasters. Android 18, with her strength and unique abilities, would be a great ally in this adventure. They might face challenges like dealing with the primitive technology of that time and also having to hide their true identities to avoid disrupting the timeline too much.
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.
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.
The contrast between them. Goku is a Saiyan hero, while Android 18 is a former villain - turned - ally. Their different origins make the idea of them falling in love fascinating.