One common theme is the contrast between their ideologies. Batman is more of a lone vigilante with a darker view of justice, while Captain America is a symbol of patriotism and upholds a more idealistic view. Fanfics often explore how they bridge this gap.
One great Batman and Captain America fanfic is 'The United Front'. It has an interesting plot where Batman and Captain America team up to fight a common enemy from another dimension. The story does a great job of portraying their different fighting styles and moral compasses while still showing how they can work together effectively.
Well, in some fanfics, they might make Captain America seem like a jerk to create an interesting plot twist. Maybe they show him being overly self - righteous or making bad decisions that go against his usual heroic image.
The Night King could be a great antagonist. His army of the dead and his own powerful magic would pose a huge threat to Captain America. Cap's used to fighting human foes, but the Night King is something entirely different.
He could also meet Odin. Odin might view Captain America as an interesting mortal from Midgard and might have some words of wisdom or a task for him to complete during his stay in Asgard.
In some fanfictions, the writers might explore what would happen if Batman was given the super - soldier serum. How would his already formidable skills be enhanced? And how would Captain America react to this new version of Batman? It could lead to some really interesting character dynamics and storylines.
One popular theme is the two heroes teaming up against a common enemy. Maybe a supervillain that's causing chaos in both Gotham and the world Captain America protects. Another theme is a clash of ideologies at first, as Batman is more of a vigilante with his own set of rules, while Captain America follows a more patriotic and military - inspired code.
For Batman, you could explore his past more deeply. Maybe in the fanfiction, he has a new revelation about his parents' death that changes his perspective. With Captain America, you could focus on how he adapts to the modern world in different ways than shown in the movies.
One idea could be a crossover where Batman and Captain America team up to take on a common enemy like a powerful alien threat. They could combine their unique skills, with Batman's detective skills and gadgets and Captain America's combat expertise and leadership.
Captain America could fit in by sharing his sense of morality and leadership. In the TOS universe, which often deals with complex moral and ethical dilemmas, his straightforward and noble values could provide a different perspective. He might be involved in diplomatic missions, using his charisma and integrity to negotiate with alien races. Also, his military experience could be applied to strategic planning during the crew's missions.