Some fanfictions explore the idea of Finn and Huntress Wizard having a relationship in secret. They have to hide it from their friends for some reason, like maybe some of their friends don't approve or there are rules against it in their society. This creates a lot of tension and interesting drama. Also, there are stories where they team up to save the Land of Ooo from a new and powerful threat, and in the process, their relationship deepens.
In some fanfictions, there's a plot where Finn and Huntress Wizard get transported to a different dimension or time period. They have to find a way back while also dealing with the new environment and the challenges it presents. It could be a more primitive time where Finn has to rely more on Huntress Wizard's skills, or a high - tech future that they both struggle to understand. This kind of plot allows for a lot of character development and exploration of their relationship.