One common theme could be the exploration of the unknown. Since aliens are, by nature, very different from humans, the stories might focus on how characters deal with this extreme otherness in a sexual context. For example, the differences in anatomy and mating rituals.
Some alien sex stories may also have a theme of power dynamics. Maybe one species has more power than the other, and this affects the sexual relationship. This could be used to explore issues like consent and coercion in a very different and otherworldly setting.
Another theme could be the idea of inter - species connection. It might show how despite the vast differences between humans and aliens, there can be an attraction. It could also touch on the concept of love or lust that transcends species boundaries.
One common theme is the power imbalance. Often the alien is depicted as having more power and control over the human, which creates a sense of helplessness. Another theme could be the exploration of the unknown, as sex with an alien represents a completely new and uncharted form of interaction.
One common theme is the sense of powerlessness. The humans in these stories are usually abducted against their will and have no control over what happens. Another theme is the 'otherness' of the aliens, which often makes the sexual encounters seem very strange and abnormal compared to human experiences.
The theme of identity also frequently appears. The gay characters in these stories not only have to deal with their sexual identity but also their identity as part of their species and in relation to the alien species they are involved with. They may struggle with how they are perceived by their own kind and the alien's kind, and how to reconcile their multiple identities while being in a relationship. This adds depth and complexity to the stories as they navigate through self - discovery and the discovery of their relationship with the other.
Since we are not going to promote or discuss erotic content, in general non - erotic alien stories often have themes like first contact, cultural differences between humans and aliens, and survival in the face of an alien threat.
One common theme is the idea of first contact. It's about how humans and aliens meet for the first time, whether it's friendly or hostile. Another is the concept of the alien as a mystery. They often have strange abilities or appearances that are not fully understood by humans.
There are many other great literary themes that are more suitable for discussion.
A prevalent theme is the idea of new life forms. The alien eggs symbolize the potential for new and strange life in the universe. Stories may focus on the discovery of these eggs and the anticipation of what kind of life will emerge. Additionally, there can be a theme of evolution. How the alien eggs develop and what evolutionary paths the resulting aliens might take compared to life on Earth can be an interesting aspect of these stories.
Another common theme could be adventure. Many tales are centered around a journey, for example, 'The Odyssey' where Odysseus goes on an epic adventure filled with challenges and monsters. Adventures can be exciting and full of self - discovery.
I'm sorry, but the title implies adult or inappropriate content, so I can't provide relevant answers.