One idea could be that Batman has to protect his baby daughter from his rogues gallery who see her as a way to get to him. For example, the Joker might try to kidnap her in a really twisted plan.
One plot idea could be that the baby doll has some sort of magical power that attracts Batman's attention. Maybe it can see into the future and warns Batman of a major threat coming to Gotham. Another idea is that the baby doll is actually a key to an ancient mystery that Batman has to solve. It could lead him on a hunt across Gotham, uncovering secrets long forgotten.
One idea could be Batman teaching Baby Robin the basics of detective work. For example, showing him how to analyze crime scenes for clues. Another could be a story where they face a villain who specifically targets Robin because he's young and inexperienced. A third idea might be a heartwarming tale of Batman protecting Robin during a city - wide disaster.
One idea could be that Batman's daughter discovers her father's identity by accident while snooping around the Batcave. She then decides to secretly train herself to be a vigilante, much to Batman's initial dismay but eventual pride.
One plot idea could be the adopted daughter discovers she has a unique power. Maybe she can communicate with animals like Batman can with bats. This new power causes some chaos as she tries to figure it out and also keep it a secret from Batman at first. Another idea is that she gets into trouble at school because of her association with Batman. Bullies target her, but she uses her martial arts training (that Batman taught her) to defend herself in a really cool way.
Well, a really cool plot might be that baby robin accidentally stumbles upon an old enemy of batman's, who doesn't realize he's just a baby. Batman then has to use all his wits to protect baby robin without the enemy finding out his true identity. Also, there could be a story where baby robin befriends an unlikely animal in the Batcave, and batman has to figure out how to handle this new situation. Maybe baby robin starts to show signs of being a tech genius at a very young age, and batman begins to train him in that aspect early on.
One plot idea could be that Batman discovers Baby Superboy and has to protect him from villains who want to use the baby's powers for evil. Maybe Batman has to figure out how to care for a super - powered baby while also keeping him safe.
One idea could be that Daryl is trying to protect his baby daughter in a post - apocalyptic world filled with new and dangerous threats. He might have to teach her survival skills from a very young age, like how to find safe water sources or identify edible plants.
One idea could be that the Joker is trying to protect his baby daughter from his enemies in the criminal underworld. He might use his unpredictable and chaotic methods to keep her safe, while also struggling with his own inner demons as a father.
A different plot might be to set the fanfiction in a modern - day context. The same basic premise of the cult's plot to have Rosemary bear the devil's child, but with modern technology and social media. Rosemary could use social media to expose the cult's activities and get help from the wider world.
Well, a possible plot is her journey to discover her own identity outside of being Snape's daughter. She could be a talented witch in a different area than her father, like divination while he was into potions. And she might have to deal with people who either idolize or hate her father, which adds a lot of drama to her life.