A frequent theme is the exploration of power dynamics. Goblins are sometimes depicted as having different kinds of power compared to humans, whether it's magical or something else. There's also the theme of forbidden love, where a human and a goblin fall in love despite the odds and the differences between their species. Additionally, the theme of adventure often comes up, as they might embark on a journey together in the story.
One common theme is the clash of cultures. Since goblins and humans usually have different ways of life, this can create interesting conflicts and resolutions. Another is the theme of acceptance, like a human learning to accept a goblin's strange ways or vice versa.
Common themes in goblin and human fanfiction include the idea of discovery. A human might discover the hidden world of goblins or a goblin might learn about the human world in a new way. Another theme is that of transformation. This could be a physical transformation, like a goblin taking on a more human - like form, or a character's internal transformation as they interact with the other species. And of course, there's the theme of survival, especially when the two species are in a situation where they have to rely on each other to survive.