Perhaps a story where a young hero is on a quest to find the origin of the monsters in order to stop them from overrunning the world. They face many challenges and meet various strange creatures along the way. They might also discover that some of the monsters are not as evil as they seem and are actually being controlled by a greater evil force.
A possible plot could be that in this world full of monsters, there is a secret society that has been secretly studying the monsters for years. The main character stumbles upon this society and gets involved in their research. They then find out that the monsters are a result of an ancient experiment gone wrong, and now they must find a way to reverse it before it's too late.
One idea could be a monster girl who is a mermaid and she has to adapt to living on land in an everyday human world. Maybe she gets a job at an aquarium and has comical encounters with visitors who don't know she's a real mermaid. Another could be a harpy monster girl trying to fit into a human school, dealing with things like flying in gym class and eating different food from what she's used to in her nest.
One idea could be exploring the backstories of the minor characters in the 'a dead world'. Maybe there was a character who had a pre - apocalypse profession that could be crucial in the new dead world, like a scientist who is now trying to find a cure for the cause of the dead world. Another plot could revolve around a group's journey to a rumored safe haven. They face various challenges on the way, including different types of undead and rival survivor groups.
One plot idea could be a new super monster arriving at the school. This new monster has a unique power that the others have never seen before. It could create some chaos at first as the other super monsters try to figure out how to get along with this new addition. Another idea is a time - traveling adventure where the super monsters go back in time to meet their ancestors and learn about their own powers' origins. And a third idea might be a mystery where the super monsters' powers start to disappear one by one, and they have to work together to find out what's causing it.
One idea could be a story where the monsters and aliens have to team up against an even greater threat from another dimension. Maybe a powerful interdimensional being that wants to conquer both Earth and the alien planets.
You could write a fanfic where the monsters swap their habitats and have to adapt to new environments. For example, a water - based monster has to live on a mountain and learn to sing in a different way due to the change in acoustics. It would be a fun exploration of how the monsters interact with new surroundings and how their music changes as a result.
Another plot could involve a mystery. The sixpence is stolen, and the protagonist has to go on an adventure to retrieve it. Along the way, they meet various characters who may or may not be trustworthy. They have to use their wits and the few clues they have about the sixpence to solve the mystery.
One idea could be a story where the inklings and octolings have to put aside their differences during a world war - like situation. They could form an alliance to fight against a common enemy that threatens both of their species. Maybe this enemy is a new type of sea creature that has been mutated by some sort of toxic waste and has a powerful army.
One idea could be exploring how the characters adapt to a world without shadows in terms of their daily activities. For example, how does the lack of shadows affect their sense of time and direction? Another plot could revolve around the discovery of a hidden realm that still has shadows, and the characters' journey to understand why it exists.
One idea could be exploring the post - Dominion world where dinosaurs are now fully integrated into society. Maybe a story about a family who has to adapt to living next to a T - Rex nesting ground. It could be full of comical and heartwarming moments as they learn to coexist.
One idea could be a human who suddenly finds themselves in an anthro world and has to learn the new social norms. For example, if it's a world of anthro animals, they might have to understand how different species interact in a more civilized way compared to the wild. Another could be a human getting involved in an adventure with a group of anthro characters to save their world from a mysterious threat.