A major theme is also the exploration of Goku's character. How he reacts to the advances and the world of Princess Snake shows a different side of him. Often, there's the theme of transformation. Maybe Princess Snake tries to change Goku in some ways, or Goku tries to change her view of the world. And of course, adventure is a big part of it as they usually embark on some sort of journey together.
One popular 'goku x princess snake fanfic' might be 'A Serpentine Love'. It often delves into the unique relationship between Goku and Princess Snake, exploring how their different worlds collide. The story usually has elements of adventure as Goku tries to navigate the world of the snake people while dealing with his feelings for Princess Snake.
Power and training. Since Goku is known for his power - seeking, his brother in fanfics often has a similar drive. They might train in unique ways or discover new forms of power.
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.
Friendship and mentorship are also common. Goku is often seen as a mentor figure to Caulifla in these fanfics. They form a bond through training and fighting side by side. Another theme could be the exploration of different universes. Given that they are from different universes in the Dragon Ball series, fanfics may play around with the idea of them exploring each other's worlds and cultures.
One common theme is growth. Both caulifla and goku are Saiyans, so fanfics often focus on their growth in power, like learning new techniques.
Another theme might be transformation or the blurring of boundaries between human and snake. Maybe the snake girlfriend has the ability to transform into a human - like form, and this creates interesting plot points about identity and acceptance.
Power and dominance are common themes. Since Goku Black was already a powerful character, in the female versions, the focus often remains on her strength and how she uses it to get what she wants.
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.