One idea could be that Harry, with his magical skills from the wizarding world, somehow gets transported to Gotham City. He teams up with Batgirl to fight a new kind of villain who is using a combination of magic and technology. Harry could use spells like Protego to shield them from attacks, while Batgirl uses her martial arts and gadgets.
Maybe Harry is on a quest to find a rare magical artifact that has ended up in Gotham. Batgirl stumbles upon him during his search. At first, they are suspicious of each other, but as they realize they are after the same goal (to keep the artifact out of the wrong hands), they start to work together. Harry could teach Batgirl some basic magic defense spells in case she ever faces a magically - powered foe again.
Perhaps a plot where Batman and Batgirl are investigating a series of strange disappearances in Gotham. They find out that it's related to a secret underground organization that is using some sort of new technology. Along the way, they start to realize their feelings for each other are deeper than just being crime - fighting partners. But they have to put their personal feelings aside to stop the organization before it's too late.
One idea could be that the OC is a new vigilante in Gotham and Batgirl takes them under her wing to train them. This could lead to a lot of action - packed scenes as they fight crime together and the OC learns from Batgirl's experience.
One plot idea could be that Supergirl and Batgirl team up to take on a new super - villain in Gotham. This villain has the ability to manipulate technology and is causing chaos. They combine Supergirl's super strength and flight with Batgirl's detective skills and martial arts expertise. Another idea is that they are transported to an alternate dimension where they have to find a way back home while facing different versions of their friends and foes. And a third idea could be that a powerful alien artifact is found in Metropolis and both girls must protect it from various forces that want to use it for evil, all while learning more about each other's worlds and abilities.
Maybe Batgirl is sent by Batman to assist Young Justice on a mission. She has to adapt to their more light - hearted and less brooding approach compared to the Bat - family. Along the way, she forms a special bond with a particular member of Young Justice, perhaps Artemis. They have to overcome their differences, like Batgirl's strict no - killing rule and Young Justice's sometimes more lenient attitude towards villains, in order to succeed.
One idea could be exploring Batgirl's internal struggle after the events of 'The Killing Joke'. Maybe she has nightmares and has to face her own fears in a new way. Another could be Batman's reaction to Batgirl's changed state of mind, and how he tries to help her without being too overbearing.
One idea could be Batgirl Beyond facing a new high - tech villain who has the ability to hack into the city's entire infrastructure. She has to use her wits and upgraded gadgets to stop him before he shuts down power and communication across the city.
Well, a plot could involve Nightwing and Batgirl preparing for the arrival of their baby in a world full of danger. They might start training their unborn child in the womb using some sort of advanced technology. And also, there could be a sub - plot where their friends in the superhero world slowly find out about the pregnancy and have mixed reactions.
A cool plot could be that there's a mysterious threat targeting all of Batman's allies. Robin and Batgirl team up to not only find out who's behind it but also to protect each other. Along the way, they share some personal stories from their pasts that bring them closer together.
Maybe Harry is the only merman in a world where mermaids are common. He faces discrimination at first but then uses his unique abilities to save the underwater kingdom from a great danger. For example, he might have a special power to purify poisoned waters that the mermaids don't have.
One idea could be that Harry Potter is magically transported to the Avengers' universe. He could use his magic to help the Avengers in battles, like creating protective shields with spells. Another idea is that the Avengers are somehow sent to Hogwarts, and they have to learn about magic while also dealing with threats in the wizarding world. For example, Iron Man might try to figure out how to integrate his technology with magic.