An interesting idea is to write a story where Catwoman discovers a secret about Batman's past that even he doesn't know. This could lead to a strange alliance between them as they both try to figure out what the discovery means. It would also add a new layer to their relationship.
You could write a fanfiction where Catwoman is framed for a crime she didn't commit. She has to prove her innocence while also dealing with the other villains in Gotham who see her as vulnerable. This would show her resourcefulness and her ability to survive in a tough situation. And of course, Batman would be conflicted about whether to help her or not.
How about a fanfiction where Catwoman has a protege? She takes a young girl under her wing and teaches her the ways of thievery and survival in Gotham. But the protege has her own ideas and might go against Catwoman's teachings, causing a rift between them. This could explore Catwoman's character from a different perspective, as a mentor.
One great fanfiction could be about Catwoman's origin story within the animated series' universe. Maybe she starts as a small - time thief in Gotham's slums and gradually rises to become the iconic cat burglar we know. She could have a complex relationship with Batman that is explored more deeply, like her internal struggle between her feelings for him and her life of crime.
One idea could be a crossover with the Teenage Mutant Ninja Turtles. Batman could team up with the turtles to take on a common enemy like the Shredder and the Joker working together. They could combine their unique fighting styles and gadgets to outwit the villains.
One idea could be creating an original character (OC) who is a new villain in Gotham. This OC could have a unique power, like the ability to control technology. They would target Batman's high - tech gadgets and try to disrupt his crime - fighting efforts.
One idea could be that Batman and Catwoman kiss during a moment of truce while they are teaming up to take down a greater threat in Gotham. Maybe they are on a rooftop, surrounded by the chaos of the city below, and in that moment of shared purpose, their feelings surface and they share a passionate kiss.
One interesting crossover idea could be Naruto visiting Gotham City. He'd be shocked by the dark and gritty environment compared to his own village. His ninja skills could help Batman in fighting villains in unexpected ways, like using his shadow clones to create distractions during a heist. Another idea is Batman somehow ending up in the Naruto world and learning about chakra. He could use his detective skills to figure out how to use it in his own unique way.
Well, perhaps a plot where Catwoman is injured during one of her heists and Batman finds her. Instead of turning her in, he takes her to his secret lair to nurse her back to health. As she recovers, they start to have long conversations about their lives and motives. This deepens their connection and eventually leads to a romantic relationship full of tension and passion, with Catwoman teasing Batman and him trying to keep his cool while being drawn to her allure.
One plot idea could be that Catwoman is on a heist and Batman tries to stop her as usual, but during the encounter, they share a moment where they realize their mutual attraction. They start secretly meeting up, away from the chaos of Gotham's crime world, and gradually fall in love. Another idea is that they are forced to work together to take down a common enemy much bigger than their usual foes. In the process, they see different sides of each other and their relationship deepens.
One idea could be that Batman and Catwoman have a daughter who discovers her parents' secret identities. She could struggle with the duality of their world and try to find her own place in it. Maybe she has her own unique set of skills that combine elements of both Batman and Catwoman.
One idea could be a story where Batman and Catwoman team up to take on a new, more powerful villain in Arkham. Maybe this villain has the ability to control the minds of the inmates, creating chaos. They'd have to use their unique skills, Batman's detective work and combat abilities, and Catwoman's agility and thieving expertise to stop the threat.
In this fanfiction, it could be interesting if Catwoman discovers a secret about the Arkham Knight that Batman has overlooked. She could use this knowledge to her advantage, either to make a deal with the Arkham Knight or to help Batman. For example, she might find out that the Arkham Knight has a weakness related to a certain location in Gotham that was important to his past. Catwoman could then lead Batman there to take down the Arkham Knight.