The theme of redemption can also be common. As I mentioned before, the idea that Cell could be swayed from his evil ways through his encounters with Goku is explored in many 'cell x goku fanfic'. This can add a layer of depth to the usually one - dimensional villain that Cell is in the original story.
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.
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.
Power is a very common theme. Fans often explore who would be more powerful in different situations or how they could combine their powers. Another theme is rivalry, as they are both powerful villains in the Dragon Ball universe. Their personalities also play a big role, with themes of pride and ego often coming up.
Another theme is power transfer or inheritance. Some fanfics might have Bardock passing on some hidden power or knowledge to Goku. This could be related to their Saiyan abilities or some special technique that only their family line can access. There is also the theme of redemption in some cases. If Bardock is brought back in a fanfic, he may seek to atone for his past actions through his relationship with Goku.
One common theme is the discovery of love. Goku, being somewhat naive in matters of the heart, gradually realizes his feelings for Launch. Another theme is adventure. They often go on quests together, which strengthens their bond.
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.
One common theme is redemption. Since Broly is often portrayed as a villain initially, many fanfics focus on his journey towards redemption with Goku's help. For example, Goku might show Broly a different way of using his power, leading Broly to change his ways.
Love and family are very common themes. Their relationship is often depicted as a strong bond that withstands Goku's adventures and battles. Chichi is usually shown as the stable presence in Goku's life, and their love story is central.
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.
Friendship is a very common theme. Their long - standing bond from childhood is often explored.
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.