What are the most popular themes in Jeff the Killer crossover fanfiction?

No, it's not really popular. Popular fanfiction usually involves more common or widely appealing themes. The idea of 'Jeff the Killer' in a 'mpreg' situation is quite outlandish and not something that would appeal to a large number of people. Most people into 'Jeff the Killer' are interested in his horror - related aspects, not male pregnancy scenarios. And those interested in 'mpreg' might be more into other types of characters or settings rather than a horror - based character like Jeff.

One common theme is the struggle between good and evil. Jane is often portrayed as more of the 'good' side trying to stop Jeff who is seen as the 'evil' one. So there's a constant battle of morals.

Another theme is often about the psychological aspect. How the female Jeff's mind works, what drives her to kill. It might also explore her backstory more deeply, like if she had some sort of trauma in her past that led her to become a killer. Fanfictions often go into detail about her inner thoughts and emotions, which makes it different from the original male Jeff the Killer concept.

Another theme is the struggle between Jeff's dark nature and his newfound feelings. His love for someone might conflict with his urge to kill. This creates a lot of internal and external drama in the stories. Like in a lot of fanfictions, Jeff has to fight his own instincts to protect the person he loves.

One popular theme could be the struggle between their dark natures and their relationship. Since they are both killers in their own right, they might have an internal battle about whether to trust and care for someone else. Another theme could be the exploration of their shared trauma that led them to become killers in the first place, and how that affects their yaoi relationship.

One popular theme is their alliance against other horror entities. They could be teaming up to fight off a new and more powerful threat that has entered their realm. Another theme could be Slenderman mentoring Jeff the Killer, teaching him how to better control his bloodlust or be more stealthy in his killings. A third theme might be them exploring a haunted location together, with each having their own motives and ways of dealing with the supernatural elements there.

One common theme is the exploration of the 'outsider' status. Since both are figures from horror, they are outcasts in a sense. Fanfictions often use their relationship to show how two beings that don't fit into the normal world can find connection with each other.

One common theme is the battle between good and evil within their relationship. Since Jeff is a killer and Jane is often portrayed as more of an anti - hero or hero figure, their interactions can be seen as a struggle between these two forces.

One common theme is fear. Since Jeff the killer is a horror character, the fanfictions often play on the reader's fear of him. Another theme is the idea of an unlikely connection. For example, the reader might be drawn to Jeff's dark side in some way.

One common theme is family. It often explores the relationship between Jeff and his sister in the context of his transformation into a killer. Another theme could be protection, like how the sister might try to protect Jeff or vice versa. Also, there's the theme of horror and how she copes with the terrifying world Jeff has become a part of.