Commissioner Gordon is another popular character. He is the link between the police force and Batman. In fanfiction, his role can be expanded, such as him taking on more risks to keep Gotham safe when Batman is not around, or his relationship with other characters like Barbara Gordon can be delved into more deeply.
One interesting plot idea could be exploring what happens to Gotham after Batman's final battle in Nolan's movies. Maybe a new villain emerges, inspired by Batman's legacy but with a more twisted view.
Batman himself is of course extremely popular. He is the central figure, and in 1939 fanfiction, people love to explore different aspects of his character, like his detective skills and his relationships.
Robin, in all his incarnations, is also a popular character in fanfiction related to Batman. He represents the sidekick aspect and the growth and development that comes with it. In Batman Beyond, Commissioner Barbara Gordon also features prominently in some fanfictions. Her connection to the original Batman era and her role in the new one can be explored in interesting ways.
Batman himself is obviously very popular. His dark and brooding nature contrasts well with the more colorful X - Men world. Also, Wolverine is often a fan favorite in these crossovers because of his tough - guy attitude.
Obviously, Batman and Spider - Man themselves are very popular. But also, characters like Robin from Batman's side and Mary Jane from Spider - Man's side often make appearances. They can add a different dynamic to the story, whether it's a romantic sub - plot or a side - kick adventure.
Catwoman often features prominently. Her complex relationship with Batman, both as an adversary and sometimes an ally, makes her a fan favorite in fanfiction. The tension between them adds a lot of drama to the stories.
Batman and Robin themselves are of course very popular. Batman's brooding nature and Robin's youthful energy make for an interesting contrast that many fans like to explore in fanfiction.
The villains are always a big draw. Characters like the Joker are extremely popular. Their chaotic and unpredictable nature makes for great storytelling in the fanfiction. Writers can come up with new schemes and interactions between the villains and Batman in this medium.
The Joker is also quite popular. When Batman's identity is revealed, the Joker's reaction can be explored in many different and interesting ways. He could either be overjoyed at finally having the upper hand or he could be disappointed because the mystery is gone.
Batman himself is obviously one of the most popular. Fans love to see how he would be written in the Arrowverse context. Another popular character would be Alfred. His relationship with Batman and his role as the caretaker and advisor always adds depth to the story. And also, characters like Catwoman might be popular as she brings in the element of mystery and romance to the fanfictions.