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 exploring Cuphead and Mugman's childhood. Maybe they had a special adventure before the events of the game. Another idea is to create a fanfiction where they meet new characters in a different part of the Inkwell Isles that has a unique theme, like an underwater world. A third idea could be a story where Cuphead has to face his fears without Mugman by his side for a change.
One popular 'baby cuphead fanfic' might be about baby Cuphead's adventures in a magical land. It could involve him making new friends and facing challenges with his innocent charm.
One idea could be a story where Snake Eyes is on a mission to retrieve a powerful artifact from Cuphead. He has to face all of Cuphead's tricky challenges and minions. Another plot could involve Snake Eyes teaming up with Cuphead to take on a common enemy that threatens their world. Maybe a powerful demon that wants to take over their land.
One idea could be a Cuphead crossover with Super Mario. Cuphead and Mugman could find themselves in the Mushroom Kingdom, facing off against Bowser's minions alongside Mario and Luigi. They could use their unique shooting skills to help in battles.
Another interesting concept is an OC that is a traveling musician in Inkwell Isles. This OC could meet Cuphead and Mugman during their travels and join them on their quests. They could use their music to soothe enemies or even as a form of attack, like creating sonic waves that stun bosses. It would add a unique element to the existing Cuphead world.
A really engaging storyline could be where baby Cuphead and Mugman are transported to a different dimension. In this new place, everything is upside down and the rules are different. They have to figure out how to get back home while also dealing with the strange inhabitants of this dimension. It could be filled with action - like running from giant bugs or making friends with a friendly but odd - looking alien - like creature.
A fanfic could focus on Dice King's backstory and how Cuphead becomes involved in it. Dice King might be reminiscing about his past and Cuphead stumbles upon him. Then, Cuphead starts to understand Dice King in a new light and they form an unlikely friendship.
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.
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.
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.