A cool plot twist might be that the city of Gotham is actually under the control of an ancient cult that has been manipulating events from the shadows. Batman starts to notice strange symbols and rituals around the city and has to not only fight the regular criminals but also this hidden, more powerful threat that has been pulling the strings all along.
Perhaps a plot twist where Bruce Wayne discovers that his father had a secret life as a crime - fighter too, but in a very different way. It could change Bruce's perspective on his own mission and add a family - related mystery to the fanfiction. This could involve finding hidden journals or messages from his father that lead him in new directions.
Perhaps the Justice League watches 'Batman Begins' as part of a team - building exercise. But as they watch, they realize that Batman's more brutal and unforgiving tactics at the start make them question if they should be more like him in dealing with certain villains. For example, Superman might wonder if he should be less lenient with Lex Luthor. This could lead to internal debates within the League.
One great example could be a fanfiction that explores Bruce Wayne's internal struggles in more depth between the events of Batman Begins and The Dark Knight. It might focus on his relationships with his allies, like Alfred. Another could be a story that delves into the Joker's origin from a different perspective, perhaps showing how he came to be in the criminal underworld before his encounter with Batman in The Dark Knight. There are also fanfictions that might imagine alternate endings to the events in these movies, such as Batman finding a different way to deal with the chaos the Joker creates.
Perhaps in the fanfiction, Batman is revealed when a new technology is used against him. Let's say a villain creates a device that can see through disguises and Batman's high - tech cowl is no match for it. This would completely change the dynamic in Gotham as all his enemies would know who he is.
One common plot twist could be Batman being betrayed by a close ally like Robin. Maybe Robin gets brainwashed by a powerful villain and turns against Batman. Another could be Batman's trusted butler Alfred being forced to betray him under some extreme threat. For example, a villain might hold Alfred's family hostage and make him leak Batman's secrets.
One great 'Batman Begins' and 'Dark Knight' fanfiction is 'The Gotham Reimagined'. It delves deep into the backstories of the characters, giving new perspectives on Bruce Wayne's journey. It combines elements from both movies in a really interesting way.
One idea could be exploring Batman's initial reaction to being part of the Justice League in a 'Batman Begins' context. Maybe he's hesitant at first, still haunted by his past traumas from 'Batman Begins' and having to learn to trust these super - powered beings. He could be constantly assessing the League's motives and methods, which could lead to some internal conflicts within the team.
One idea could be exploring Bruce Wayne's early training in more detail. Show his struggles and how he overcame them. For example, his first encounters with Ra's al Ghul's League of Shadows could be more in - depth, with new challenges and characters added.
One idea could be that the OC is a childhood friend of Bruce's who has a unique skill, like being an expert in ancient martial arts from a far - off land. They could influence Bruce's training and view on justice in a different way. For example, they might introduce him to more spiritual aspects of combat and self - discovery.
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.
Here's a plot twist: Batman and Miss Martian are on a mission, and they find out that the whole situation was set up by a higher power in the superhero community to test their loyalty to each other. They have to decide whether to continue to trust each other and fight against the system that is trying to manipulate them.