One idea could be that PB accidentally creates a magical device that swaps their personalities. Marceline then has to deal with being super sweet and girly while PB tries to maintain her tough rocker image. It would lead to a lot of comical situations as they try to navigate their daily lives in each other's shoes.
Their relationship could be developed through music. Marceline could teach PB how to play the guitar, and in the process, they open up to each other about their past traumas. PB might share her insecurities about ruling the Candy Kingdom, and Marceline could talk about her loneliness as a vampire.
The writing style matters a great deal. A great Marceline x PB fanfic uses vivid descriptions to bring the characters and their world to life. It might describe Marceline's cool, edgy style and Princess Bubblegum's scientific - mindedness in a way that makes the readers feel like they are right there in the Land of Ooo with them.
One great 'Adventure Time PB and Finn Fanfiction' is 'The Unlikely Bond'. It beautifully explores the friendship between PB and Finn in a new adventure where they have to solve a mystery in the Candy Kingdom. The story is full of the charm and humor that the show is known for.
The plot needs to be engaging. It could be a new adventure in Ooo, like exploring an uncharted part of the Land of Ooo or dealing with a new magical problem. It also helps if there are some emotional elements, like a conflict between PB and Finn that they have to resolve, which deepens their relationship.
One popular theme is friendship exploration. Since PB and Marceline have a complex relationship in the original work, fanfictions often delve deeper into how their friendship could develop in different scenarios.
Some Tumblr blogs dedicated to Adventure Time might also have or recommend 'pb x marceline' fanfic. These blogs often have a community of fans who are into creating and sharing fan - made content. You can search for relevant tags like #pbxmarceline or #adventuretimefanfic to narrow down your search.
You can try websites like Archive of Our Own (AO3). It has a large collection of fanfictions. Just search for 'pb x marceline' there, and you'll likely find many interesting stories.
You can try searching on fanfiction websites like Archive of Our Own (AO3). There are often many well - written Marceline x PB fanfics there. Just use the search function and type in the relevant tags.