One interesting fanfiction could be about Bella having special powers that Carlisle discovers and they go on a journey to understand them. It might involve them traveling to different vampire covens to seek knowledge.
There could be a fanfiction where Bella and Carlisle form an unlikely friendship in the absence of Edward. They bond over their love for medicine and knowledge, and Carlisle teaches Bella about the history of vampires in a more detailed way than she had known before. This could lead to a whole new adventure in the vampire world for Bella.
One great fanfiction could be 'The Unforeseen Bond'. It delves into a different kind of relationship between Bella and Carlisle, where they form an unexpected friendship that has a profound impact on the Cullen family dynamics. Another one might be 'A New Perspective' which shows Bella's view of Carlisle as a mentor figure rather than just Edward's father. And then there's 'Carlisle's Concerns', which focuses on Carlisle's internal thoughts regarding Bella's presence in their vampire world.
A plot could revolve around Carlisle and Bella going on a secret mission together. Maybe they have to find a lost ancient vampire artifact that could change the future of the vampire world. Along the way, they develop a deep bond and respect for each other.
Another fanfic could be 'The Unforeseen Alliance'. In this, bella and carlisle find themselves in a situation where they have to team up against a common enemy. It's full of action and also shows the growth of their relationship as they learn to trust each other more.
One common theme is the exploration of a forbidden relationship. Since Carlisle is much older and in a different position in the vampire hierarchy compared to Bella, it creates an interesting dynamic. Another theme is the idea of mentorship. Carlisle often acts as a mentor figure to Bella, guiding her through the vampire world.
Fanfiction.net is a really popular platform for 'bella swan and carlisle cullen fanfic'. It has a large collection of stories, ranging from different genres and writing styles. You can easily search for specific tags related to bella and carlisle to find the fanfics you're interested in.
There's 'A Different Path'. This fanfic takes a unique turn where Bella discovers she has some special abilities that Carlisle is intrigued by. It's filled with mystery and some really cool plot twists that keep you hooked from start to finish.
You can start by looking on Fanfiction.net. It has a large collection of Twilight - related fanfictions, including many that focus on Bella and Carlisle. Archive of Our Own (AO3) is also a great place. It has a wide variety of fan - created works, and you can easily search for specific pairings like Bella Swan and Carlisle Cullen.
One interesting fanfiction could be about Bella and Alice going on a shopping spree together in a human - vampire friendly town. They could bond over choosing outfits and sharing fashion tips, which is quite different from the usual intense situations in the original series.
One interesting fanfiction could be where Emmett and Bella go on an adventure in the forest that's not part of the original story. In this fic, Emmett shows Bella some secret spots known only to the Cullens. It's a story full of discovery and newfound friendship between them.
Their relationship can be developed through shared experiences. For example, they could face a common enemy together. This would force them to rely on each other and understand each other's strengths and weaknesses.