One possible storyline could be a team - up against a powerful new villain in Gotham. Power Girl's super - strength and flight combined with Batman's detective skills would make for an exciting adventure. They could start off not trusting each other fully, with Batman being cautious of Power Girl's more brash and powerful approach, but as the story progresses, they learn to work together effectively.
One interesting storyline could be Power Girl and Batman teaming up to take on a powerful new villain in Gotham. This villain could be someone with the ability to manipulate time, causing chaos in the city. Power Girl's super strength and flight, combined with Batman's detective skills and gadgets, would make for an exciting battle.
One interesting storyline could be a team - up against a powerful new villain who is threatening both their worlds. They combine their unique powers, like Power Girl's super - strength and flight with Wonder Woman's combat skills and Lasso of Truth, to take on the baddie.
One possible storyline could be Harley trying to reform and Batman being skeptical at first. For example, Harley could start doing small good deeds in Gotham, like helping out at an orphanage. Batman would be watching her closely, waiting for her to slip back into her old ways. Another idea is a story where Harley has some information that could help Batman take down a major villain, but she wants something in return, like a chance at a new life outside of Arkham Asylum.
One interesting storyline could be a team - up against a new super - villain who has the power to manipulate time. Batman and Batwoman would have to race against the clock to stop this villain before he changes history to his advantage.
One interesting storyline could be them teaming up against a common enemy from another dimension. They both have unique powers and skills, so seeing how they combine their abilities to fight would be great.
One interesting storyline could be exploring how Batman got his scars in a different way than the traditional origin. Maybe in a fanfic, he gets the scars while protecting a young orphan who later becomes his sidekick. Another could be a story where the scars are a source of new powers or a connection to an ancient prophecy.
One common theme is the clash of their different personalities. Batman is dark and brooding while Power Girl is more confident and outspoken. Their interactions often revolve around how they deal with this difference.
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.
Perhaps there could be a storyline where the baby is actually a key to saving Gotham in the future. Batman and Batgirl discover this and have to raise the baby in a way that will prepare it for its important role. They face many challenges along the way, including trying to keep the baby's identity a secret from their enemies.
One interesting storyline could be about a new Mew Mew character who has unique powers that are different from the original ones. For example, she might be able to control water in addition to the typical animal - based powers. This could lead to new challenges and adventures as the team has to adjust to her presence and figure out how to use her powers effectively.