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.
Another plot could involve the Female Joker forming an alliance with other villains, but Batman discovers that she has her own hidden motives within the alliance. She might be secretly planning to double - cross them all and take over Gotham's underworld herself. Batman has to figure out how to use this to his advantage while also dealing with her unpredictable nature.
One idea could be that the deaged Joker, now with a child's body but his same devious mind, tries to manipulate the younger version of Batman into believing they are friends while secretly setting up traps. Another could be that the deaged Joker's actions cause Batman to re - evaluate his own origin story and how it might be related to this new, younger - but - still - dangerous foe. Or perhaps the deaged Joker forms an alliance with other deaged villains in Gotham, creating chaos that Batman has to stop.
One interesting plot idea could be a fanfiction where the Joker somehow comes back to life in Arkham Knight. Maybe he was only in a coma and wakes up with a new, even more deranged plan to take over Gotham. He could start by manipulating the inmates in Arkham again, creating chaos from within the asylum.
One idea could be that Rachel, instead of being in a typical relationship with Batman, has a series of mind - games with the Joker. The Joker tries to use Rachel to get to Batman in a more psychological way, like trying to make her question Batman's methods. Another plot could be that Rachel discovers a hidden connection between Batman and the Joker from their past, which changes her perception of both of them.
One plot idea could be that the Joker is in a situation where he's being hunted by a more dangerous criminal group, and Batman, despite their long - standing enmity, saves him because he realizes the chaos that would ensue if the Joker fell into the wrong hands. Another could be that the Joker has some information vital to Gotham's safety, and Batman has to rescue him from a hostage situation to get that information. Maybe the Joker is poisoned, and Batman has to find an antidote and save him in order to also stop the spread of the poison throughout Gotham.
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 idea could be exploring a world where Batman and Joker have to team up against a greater evil. Maybe a powerful alien force arrives in Gotham and they realize they need to combine their skills, even if reluctantly.
One plot idea could be that the Female Joker is trying to prove herself to Batman as a worthy adversary. She sets up elaborate schemes that are more about psychological warfare than physical harm. For example, she targets Batman's allies, not to kill them but to make them question their loyalty to Batman.
A plot could involve the Joker creating a new type of toxin that doesn't just affect people's physical state but also their perception of reality. Batman has to race against time to find the antidote while also dealing with the chaos in Gotham caused by the affected citizens. Or perhaps a story where the Joker discovers Batman's true identity in a very unexpected way and uses it to manipulate those closest to Bruce Wayne, forcing Batman to face a whole new level of personal and public danger.
Another plot idea could be that the looking glass is a portal to different versions of Gotham City. Batman and Joker are constantly shunted between these versions. In some, they are friends, in others they are mortal enemies with even more extreme versions of their personalities. They have to figure out the rules of this looking - glass world to stop it from collapsing all the versions of Gotham together.
In some fanfictions, a plot twist could be that Batman discovers the Joker has a family or a past that explains his madness in a more sympathetic way. For example, if it's revealed that the Joker was once an ordinary man who was experimented on by a corrupt organization, and Batman has to decide whether to still see him as a pure villain or something more complex. This could change the way they interact in the story.