One interesting storyline could be them teaming up against a new supervillain that neither can defeat alone. They combine their unique skills, Superman's super strength and flight with Batman's detective skills and gadgets.
In some fanfictions, they might have a falling out over a moral dilemma. For example, Superman wants to use his powers more openly to help people, while Batman believes in a more covert approach. This creates tension but also shows their different personalities and how they can work through it to remain friends.
One interesting storyline could be a team - up against a powerful new villain that neither can defeat alone. They have to combine their unique skills, like Superman's super strength and Batman's detective skills.
In some Mpreg fanfictions, there could be a storyline where Batman and Superman have to figure out the genetics of their unborn child. Given their different origins - one being a Kryptonian and the other a human with no super - powers originally - it would be fascinating to see how their child might inherit or combine their abilities. There could also be a plot where they have to deal with time - traveling villains who try to prevent the birth of their child for some evil purpose.
A cool story could be about them having a friendly competition to see who can solve a series of mysterious crimes in the other's city first. Along the way, they learn more about each other's methods and develop a deeper respect for one another. This also gives an opportunity to explore the different atmospheres and challenges of Gotham and Metropolis.
One interesting storyline could be a young Superman and Batman teaming up for the first time in a kid - friendly adventure. Maybe they are trying to stop a group of small - time villains who are stealing toys from all the kids in Gotham. They use their unique powers and detective skills respectively to track down the bad guys and return the toys.
One interesting storyline could be a redemption arc for Superman. In the Injustice universe, Superman has gone down a dark path. A fanfiction might explore how Batman tries to bring back the good in him, with lots of emotional confrontations and moral debates between the two.
One great example could be a fanfiction where Batman and Superman team up to face a new, powerful villain that neither could defeat alone. They combine their unique skills, with Batman's strategic mind and Superman's super strength, to outwit the bad guy. Another example might be a story that delves into their friendship during their off - time, like when they have a friendly sparring session to keep each other on their toes. There are also fanfictions that explore how they support each other through personal crises, like when Superman has doubts about his place on Earth and Batman is there to offer his grounded perspective.
One possible storyline could be that Batman has to use his detective skills to find out a hidden threat to Superman before saving him. Maybe there's a kryptonite - based weapon that only Batman can detect and disable.
Often it starts with mutual respect. They recognize each other's abilities and dedication to justice. For instance, Superman respects Batman's ability to fight crime without powers, and Batman respects Superman's selfless use of his powers.
One popular storyline could be them teaming up against a common enemy that is too powerful for either of them alone. For example, a new super - villain who has the power to manipulate time. They have to combine their skills, Batman's detective skills and Superman's super strength and flight, to figure out how to defeat this villain. Another storyline might involve them having a falling - out over their different methods of protecting the city, and then having to reconcile in order to save the world from a cataclysmic event. There could also be a story where they discover they are long - lost brothers in a more in - depth way, exploring their family history and how it impacts their relationship.
One interesting storyline could be a reimagining of Batman's first encounter with the Joker in the 1939 fanfiction context. Maybe the Joker starts as a small - time criminal and Batman has to figure out his true motives early on.