One common theme is the exploration of fear. Female characters often experience extreme fear when encountering Jeff the Killer, and the fanfic delves into how they cope with that fear, whether it's by fighting back or succumbing to it.
Love - hate relationship is also very common. They are enemies by nature but in some fanfics, there's an underlying attraction or connection that they can't deny. This creates a lot of drama and tension in the stories.
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.
One common theme could be the struggle between good and evil, especially considering Pinkamena's somewhat ambiguous moral standing and Jeff the Killer's clearly villainous nature. Another might be the idea of redemption or the lack thereof in their relationship. Also, themes of madness and chaos often come up as both characters are associated with rather unhinged behaviors.
Isolation is also a theme that might come up. Both characters are often depicted as being alone in their own terrifying worlds. In the fanfic, their meeting could either break that isolation or intensify it. And there's the theme of the unknown. The reader is always left wondering what these two will do next, especially when their powers and motives are so unclear.
One common theme is the power struggle. Since both Jeff and Nina are killers, there can be a battle for dominance in the fanfic. Also, the theme of unrequited love sometimes pops up, with Nina loving Jeff but not always getting the same in return. And of course, the general horror theme of blood and gore is often there as it's part of their nature as killers.
One common theme is the exploration of the dark side of human nature. Since both Jeff the Killer and Ben Drowned are from rather dark and disturbing origins, their stories often delve into this aspect.
One common theme is the power dynamic. Jeff is often portrayed as the dominant and menacing force, while Sally is more of the victim or the one trying to resist his dark influence.
A prevalent theme is the idea of an unlikely partnership. Given their different natures, fanfics often play around with how they might come together, whether it's for mutual survival or some other strange reason. For instance, they might team up against a more powerful evil in their world. It also explores the power dynamics between them, as Jeff is more impulsive while Eyeless Jack is more calculating. Another theme is the psychological aspect of their relationship. How do their minds, which are both damaged in their own ways, interact? Do they find some sort of understanding or is it just a constant battle of wills? This is often explored in great detail in many 'eyeless jack x jeff the killer fanfic'.
One common theme is redemption. Given their dark and violent pasts, many fanfictions explore the idea of either Jeff or Jane seeking redemption through their relationship. Another theme is the power of love to change, as they are two very damaged individuals and love might be the thing that can transform them.
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.