They could have a story where there is a misunderstanding between them. Caspian thinks Peter is trying to take over his leadership in Narnia, and Peter is just trying to help. This causes a rift between them that the enemies of Narnia try to take advantage of. But in the end, through a series of events and honest conversations, they realize their mistake and work together again to save Narnia.
A great plot could be a time - travel related one. Maybe something goes wrong in Narnia, and Peter and Caspian are sent back in time to the very beginning of Narnia's creation. They have to figure out how to get back to their own time while also making sure that the events that led to Narnia's creation still happen as they should. They meet all kinds of ancient beings and learn secrets about Narnia that no one else knows.
One idea could be that Peter gets lost in the forest of Narnia on his own during a quest and has to rely on his wits and some unexpected help from a minor character in the Prince Caspian story to find his way back to the main group. Another could be a time - travel twist where Peter is sent back to a crucial moment in Prince Caspian's past and has to figure out how to change things without disrupting the future of Narnia too much. And perhaps a story where Peter and Prince Caspian have a misunderstanding that leads to a mini - adventure to resolve their differences and strengthen their bond.
One idea could be a story where Peter and Caspian have to go on a secret mission together to find a lost magical artifact that can save Narnia from a new threat. They start off not getting along but gradually learn to respect each other's skills.
Some fanfictions focus on the relationship between Peter and Caspian when they first meet. It could explore how they initially view each other with suspicion, being from different worlds in a way. But as they start to understand each other's motives and the importance of their roles in Narnia, they form a strong bond that helps them protect Narnia from various threats.
One idea could be that Susan returns to Narnia during a time of great peril, and she and Prince Caspian have to team up to defeat a new, powerful enemy. They might discover hidden powers within themselves along the way.
One plot idea could be that they are separated during a battle in Narnia. When they are reunited, the relief and joy lead to a passionate kiss. This kiss could symbolize their new - found determination to never be parted again and fight side by side.
One idea could be that Susan returns to Narnia in a time of great need, and she and Prince Caspian have to work together to defeat a new, powerful enemy. Maybe they discover an ancient magic that only they can unlock through their combined efforts.
One idea could be that the baby has a special power. For example, the baby might be able to communicate with magical creatures in a way that no one else can. This could lead to all sorts of adventures as Lucy and Caspian try to protect the baby from those who might want to use the power for evil.
One idea could be that Lucy discovers a hidden magical ability that helps Prince Caspian in a crucial battle. For example, she might be able to communicate with the spirits of the forest in a way that no one else can, and these spirits provide strategic advice to defeat an enemy. Another plot could involve Lucy getting lost in a mysterious part of Narnia and Prince Caspian embarking on a quest to find her, during which they both learn more about each other's pasts and grow closer.
One plot idea could be that Fem Harry Potter somehow gets transported to the world of Narnia during the time of Prince Caspian. She could use her magic skills, learned from Hogwarts, to help Caspian in his battles. For example, she might use spells like Protego to shield his army from enemy attacks.
Maybe there could be a plot where an evil force in Narnia is trying to separate them. Lucy and Caspian have to go on a dangerous journey together to stop this force. Along the way, they rely on each other's strengths. Caspian protects Lucy from physical threats while Lucy uses her magic to solve various puzzles. Their bond grows stronger through these trials and they eventually confess their love.