Adventure is a big theme as well. Given Goku's love for fighting and exploring, and Mera's own adventurous spirit in some interpretations, they embark on all sorts of quests in fanfics. They could be searching for a lost artifact or trying to stop an evil force from taking over a particular realm.
The theme of love against all odds is also quite prevalent. Given their different origins and the fact that Goku is already married in the original story, their relationship in fanfics has to overcome many obstacles. This could be social, moral or even physical (like dealing with other powerful characters who oppose their union), but they still find a way to be together, which makes for an interesting read.
The theme of power is also prevalent. Their combined power or the pursuit of greater power individually can be a central focus. Some fics might have them training to reach new levels of power, like achieving new Super Saiyan forms, which is very exciting to read about.
A common theme is rivalry - turned - friendship. Given their history in the original story, many fics explore how they can move past their animosity.
One common theme is the clash of their different cultures. Goku is from a more action - oriented, martial - arts based Saiyan culture, while Diana is from the Amazonian culture. Their interactions in fanfics often explore how these two very different cultures can coexist or influence each other.
Common themes include the father - son relationship. This is explored in different ways like Goku's absence at times and how it affects Gohan and then how they reconnect. Another is the exploration of Gohan's potential. Goku is usually there to unlock that potential. There are also themes related to the Saiyan culture. How Goku passes on knowledge about their race to Gohan and how Gohan uses that knowledge in battles and in life.
One common theme is redemption. Frieza is often portrayed as having a chance at redemption through his interactions with Goku. For example, in some fanfics, Goku's unwavering belief in the good in people (or in Frieza's case, beings) starts to make Frieza question his own evil ways.
One common theme is the clash of ideologies. Goku is all about protecting the innocent and having a fair fight, while Cell is more about self - preservation and domination at first.
One common theme is the clash of cultures. Goku comes from a world of martial arts and honor, while Revy is from a more violent and lawless world. Their coming together often leads to exploring how these different backgrounds interact.
One common theme is the power of friendship. Despite their differences, Goku and Bulla often form a deep bond in fanfics. Another theme is adventure. They usually go on some kind of exciting journey together, like searching for a powerful artifact or saving the world from a new villain.
One common theme is rivalry - turned - friendship. Their long - standing rivalry in the original series is often explored in fanfics as a starting point that then evolves into a deeper connection.