Well, the idea of hope is a big theme. Despite the difficult situation of the alien blockade, the characters in the fanfics don't give up hope. They keep fighting and looking for solutions. Also, the theme of sacrifice is there. Some characters may sacrifice themselves for the greater good, for the sake of breaking the alien blockade or saving others.
One common theme is the exploration of the unknown. Since it involves an alien pregnancy, there's a lot of mystery about how the pregnancy will progress, what the alien offspring will be like, etc. Another theme is the isolation of the pregnant character. Often, they are alone in their situation, not fully understood by others.
One common theme is human survival. It's all about how humans find ways to stay alive during the alien invasion.
The theme of acceptance is also quite common. As the alien performs on the stage, they gradually gain acceptance from the human audience or other performers. It can be a story of breaking barriers and building relationships between different species in the context of the stage environment.
One common theme is transformation. The obvious one is the physical transformation during the alien metamorphosis, which can be both fascinating and terrifying. Another theme is survival. Characters often have to struggle to survive in the face of the unknown changes brought by the metamorphosis. And there's also the theme of discovery, as they discover new abilities or aspects of themselves during the process.
Another theme is survival. Being abducted is a dangerous situation, and the characters usually have to fight for their lives. They may face threats from the aliens or the harsh conditions of the alien spacecraft. In some fics, the humans have to outwit the aliens to survive.
One common theme is the exploration of differences. Since it involves an alien, there are differences in biology, culture, and values. For example, how an alien might show affection could be very different from a human. Another theme is acceptance. The characters usually have to accept each other's uniqueness to build an intimate relationship.
Another common theme is the mystery surrounding the two species. Fanfics often explore the origin and motives of the aliens and predators in more depth. For example, some stories might delve into why the predators hunt the aliens. It adds an extra layer of intrigue to the already complex relationship between the two.
Another theme is heroism. The OCs usually show great courage and determination in the face of the alien threat. They might take on dangerous missions, like infiltrating an alien base, to save humanity. It's about rising to the occasion and being a hero in a world on the brink of destruction.
Well, in alien impregnation fanfic, a frequent theme is the clash of cultures. You've got the human culture and the completely alien one. When impregnation occurs, it can bring up all sorts of issues like how the two species will co - exist, especially when there's a new life form involved. Also, the theme of survival is there. The human may have to figure out how to survive in a world where she or he is carrying an alien offspring.
A major theme is adaptation. The characters in 'alien body swap fanfic' have to adapt to new physical forms and abilities. For example, an alien in a human body might be confused by our limited senses compared to their own. Also, the theme of discovery is common. They discover new things about themselves and the other species during the swap. It can be a journey of self - discovery as well as learning about the other.