Perhaps in the fanfiction, the Female Joker creates a series of mind - bending illusions across Gotham. Batman has to navigate through these illusions to find the real her and stop her from causing more chaos. Along the way, he starts to question his own sanity as the Female Joker's games get more and more intense.
Another plot could involve Fem Batman and Joker in a sort of cat - and - mouse game where the Joker is specifically targeting Fem Batman because she's a woman. He might underestimate her at first, but she proves to be just as formidable as the male version. This would explore themes of gender and power in the Batman - Joker dynamic.
A plot could involve the reader having a special ability that both Batman and the Joker are interested in. Batman wants to use it for the good of Gotham, while the Joker wants to corrupt it for his own amusement. The reader has to navigate between these two very different forces, and in the process, discovers more about themselves and the nature of good and evil in Gotham.
A plot where they are friends in a post - apocalyptic Gotham is really engaging. In this world, they have to work together to survive against new threats like mutant gangs. Batman tries to bring some order while the Joker brings his unique brand of survival skills. Their friendship is tested as they have to deal with limited resources and moral dilemmas.
Another plot might involve the Joker facing a new rival in the criminal underworld, and Harley Quinn has to choose between staying loyal to the Joker or making her own path. This could lead to a lot of drama and action, like Harley using her acrobatic skills and unique weapons to fight the new threat while dealing with her feelings for the Joker.
In some fanfiction, the Female Joker might have a different origin story than the male one. For example, she could be a victim of a corrupt system who turns to chaos as a form of revenge. This could lead to an interesting dynamic with Batman, who is always fighting for justice in a more traditional sense. Batman may struggle with whether to help her or stop her, adding depth to their relationship in the story.
Well, sometimes in such fanfiction, there are alternate universes. For example, a world where the Joker and Batman have to team up against a greater evil. This flips their typical dynamic on its head and makes for an exciting read.
One interesting story could be where Joker tries to turn Gotham against Batman in a very psychological way in the fanfiction. He spreads rumors and false evidence to make the citizens doubt Batman's motives.
One interesting plot could be Harley Quinn trying to reform and Batman being skeptical at first. For example, she might start to help Batman take down some minor villains as a way to prove herself. Another plot could involve a team - up where they have to face a new, powerful enemy that neither could defeat alone. Maybe a villain who has the power to manipulate minds and they have to work together to resist the control.
Some fanfictions might focus on the psychological aspects of their relationship. The Joker's insanity and Batman's unwavering sense of justice create a really unique dynamic. In slash fanfiction, this could be explored in terms of how they understand each other on a deeper level, perhaps a level that no one else can fathom.
One interesting story could be where Joker captures Batman and tries to break his spirit by showing him a distorted Gotham City that he has created in an abandoned area. Joker might use his henchmen to taunt Batman while he's trapped, but Batman uses his wits to find a way out and turn the situation around on Joker.