One common theme is the epic battles. Fans often write about Godzilla Earth facing off against other powerful monsters in intense combat.
A prevalent theme is the power dynamic between them. Sometimes the male Godzilla is depicted as the stronger one, but in some fanfictions like 'The Equal Partners', they are shown as equals in terms of strength and intelligence. Also, the theme of discovery is common. For example, in 'The Discovery of a New Bond', they discover new aspects of their relationship and their own abilities as they face various challenges together. Love and loyalty also play a big part in many of these stories, especially in ones that focus on their relationship on a more emotional level.
One common theme is protection. Godzilla is often depicted as protecting baby Godzilla from various threats, be it other monsters or human interference. Another theme is growth, showing baby Godzilla's development into a more powerful creature over time.
A lot of fanfiction delves into the scientific aspects of Godzilla. Given that it's a giant, prehistoric - like creature, there are stories that try to explain its biology, its powers from a scientific perspective. Some might even come up with theories about how Godzilla could co - exist with modern - day ecosystems. Also, the idea of Godzilla as a symbol, either of destruction or hope, is a theme that runs through many fanfictions.
You can try some popular fanfiction websites like FanFiction.net or Archive of Our Own. They usually have a wide range of fanfictions including those related to Godzilla Earth.
A common theme is the clash of two different power scales. Godzilla is a huge, destructive force, while Pokemon have their own unique powers. So, there's often a theme of how these two types of power interact. Another theme could be the idea of an outsider (Godzilla) in the Pokemon world, and how the Pokemon and trainers react to this strange and powerful being.
Power is a common theme. Since Godzilla is already a powerful figure, when it's a female, it often explores how she wields that power differently. Another theme is motherhood, as mentioned before, like how she might care for offspring or be a protector in a maternal way.
Since I haven't actually read such fanfiction, it's hard to say for sure. But perhaps themes could include the challenges of a pregnant kaiju, how the other monsters in the Godzilla universe react, or the idea of a new kind of monster being born.
One common theme is power. Godzilla is extremely powerful, and in the DxD universe which also has powerful characters, exploring how his power compares and interacts is a big theme.
Well, a frequent theme is the exploration of Godzilla Jr.'s powers. In the context of Godzilla Final Wars, the fanfiction might show how he discovers or hones his abilities. Also, the theme of family can be present, as Godzilla Jr. has a connection to the larger Godzilla family. And there could be themes of survival and heroism as he faces the many threats in the Godzilla Final Wars universe.
Godzilla Earth is not a fanfic. It has its own official production and creative process, distinct from fan-created works. It's a legitimate entry in the Godzilla canon.