One common theme is adventure. Since they are characters from Narnia, the stories might involve them going on adventures while taking care of a baby. Maybe they are on a quest and have to protect the baby at the same time.
Well, Archive of Our Own (AO3) is also a good source. Some of the Caspian and Lucy baby fanfiction on there might explore their relationship in a really cute way. For example, there could be stories where they take care of a baby together in Narnia, which shows their characters growing and developing in a new situation.
The relationship between the baby and the other characters in Narnia could also be developed. The baby might befriend the talking animals like Mr. Tumnus. This friendship could make the baby more connected to the world of Narnia, and also make the other characters more protective of the baby. As a result, Lucy and Caspian would have more interactions with these characters, strengthening their relationships in the process.
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 common theme is adventure. Given their backgrounds in the Narnia stories, fanfictions often send them on new quests. For example, they might explore uncharted parts of Narnia or other magical realms.
Fanfiction can provide a sense of continuation. Since their own story might have ended, fanfiction gives them the opportunity to be part of new tales, with new challenges and emotions. It also lets them explore aspects that weren't fully developed in the original story, like their deeper friendship or potential romantic feelings.
Romance is also a big theme. Writers like to explore the potential relationship between Caspian and Lucy. They might write about how their feelings for each other develop over time, from initial admiration to deep love. It could involve cute moments like sharing a secret in a hidden garden in Narnia.
A common theme is the 'forbidden love' aspect. Since they come from different worlds in the original stories, fanfictions often play on the idea that their love is something that goes against the norm or is difficult to pursue. Another theme is the 'growth through love'. Their relationship helps them both grow as individuals, with Lucy becoming more confident and Caspian becoming more open - hearted.
One common theme is the exploration of different cultures. Since Lucy is from one part of Narnia and Caspian has his Telmarine roots, their marriage often involves melding these two different ways of life.