One idea could be that the baby in the castle has some special powers. For example, it can communicate with the castle's spirits. Another could be a story where the baby is a lost heir to the castle's throne and there are various characters trying to protect or use the baby for their own gain.
In a 'castle baby fanfic', you might consider a scenario where the baby is found in the castle by a kind-hearted knight. The knight then decides to take care of the baby. As the baby grows, it shows an extraordinary aptitude for learning about the castle's history and defenses. This could lead to a story where the baby, now a young child, helps defend the castle from an approaching enemy army by using its unique knowledge of the castle's secrets.
A cute plot could be that their baby is born during a big case. Castle is away when Beckett goes into labor, and he has to race back. When he finally arrives at the hospital, he is just in time to hold their new - born, and they both realize how their lives are about to change in the most wonderful way.
One idea could be a story about a young adventurer who discovers a hidden passage in Bast Castle. They then embark on a journey to find out what secrets the passage holds, perhaps leading to a long - lost treasure.
One idea could be a mystery within the Arcadia Castle. Maybe a valuable artifact has gone missing and the main character has to search through the castle's many hidden passages and rooms to find it. Another could be a love story set against the backdrop of the castle's grandeur, with two characters from different social classes falling in love while attending a ball at the castle.
One idea could be a story where baby peridot discovers a hidden magic in the forest. It stumbles upon a glowing crystal that gives it the power to communicate with animals. Then it goes on an adventure with its new animal friends to find the source of the crystal's magic.
Perhaps a 'Cuphead baby fanfic' could explore the origin of Cuphead as a baby. Was he born with his powers? Or did he acquire them in a special event when he was a baby? The fanfic could also show baby Cuphead's relationship with the Devil in a more comical and innocent way, like the Devil being both annoyed and amused by this tiny, fearless baby.
One idea could be a story where Baby Kirby discovers a new kind of power. For example, he might find a special star that gives him the ability to fly faster than ever. Another idea is a fanfic where Baby Kirby befriends a lost little creature in Dream Land and they go on an adventure together to find the creature's home. Or perhaps a story where Baby Kirby accidentally enters a strange, magical realm and has to figure out how to get back home while facing various challenges along the way.
One idea could be to explore a different timeline within the Castle universe. Maybe a scenario where the characters face a threat that changes their relationships in unexpected ways. For example, Castle and Beckett could be transported to an alternate reality where they are on opposite sides of the law, and the story could revolve around how they come to terms with this new dynamic and find their way back to each other.
Another plot idea could involve a quest within the castle. For example, a character is searching for a hidden treasure or a magical item that is said to have the power to save the castle from an impending doom. They would have to face various challenges and puzzles along the way.
One idea could be a story where the phantom has a protective instinct towards the baby. Maybe the phantom is a misunderstood entity and the baby is the only one who isn't afraid of it, so it decides to safeguard the little one from all the evils in its spooky world.
A great plot for a 'baby daddy fanfic' could be that the baby daddy is a struggling artist. He and the mother had a passionate relationship in art school. Years later, he's still trying to make it big when he discovers he has a child. He then has to balance his pursuit of art with his responsibilities as a father. He might use his newfound fatherhood as inspiration for his art, and along the way, he and the mother re - explore their relationship while dealing with the joys and challenges of raising a child.