No. There are so many different takes on Finn and Marceline in fanfiction. Their relationship can range from a mentor - mentee type where Marceline imparts her wisdom to Finn, to a simple acquaintance - type relationship. Just because they are popular characters together doesn't mean all fanfictions will make their relationship romantic.
Simon, if he makes an appearance in the fanfiction, would have a very different dynamic with Marceline. He has a long history with her and his wisdom could play a crucial role in helping her understand and manage her 'vampire in heat' situation. His presence could also bring up a lot of memories for Marceline, which would add depth to the story.
Finding a good 'pregnant Marceline fanfic' can be a bit of a hunt. You might start by asking in fan groups dedicated to the show or character. People in those groups often share their favorite fanfics. Also, keep in mind that the quality can vary widely, so be prepared to sift through a few to find a really engaging one.
I really like 'Finn and Marceline's Night Out'. In this fanfic, they have a sort of double - date situation with Jake and Lady Rainicorn which leads to some really funny and heartwarming moments. It shows a different side of their relationship in a more comical setting.
Some Marceline fan fictions focus on her past. Maybe a story about her early days as a vampire, how she came to be friends with Simon (the Ice King). It could show her struggles and growth, like how she learned to control her vampiric urges and how her friendship with Simon influenced her view of the world. This type of fan fiction can be really fascinating as it delves into the untold parts of her backstory.
The Ice King and Marceline have a complex relationship in Adventure Time. The Ice King is often a bit of a nuisance, but Marceline, being a vampire, has her own unique way of dealing with him. Sometimes they're at odds, like when the Ice King's crazy schemes disrupt Marceline's laid - back vampire life. But other times, there's a strange sort of understanding between them.
The popularity of Finn and Marceline as a couple in fanfiction stems from multiple factors. In the source material, they have a unique bond. Finn's pure - heartedness and Marceline's edginess create a fascinating contrast. Their relationship is also one that can be developed in many different ways. Fanfiction writers are drawn to the idea of exploring how Finn's heroic nature might be influenced by his love for Marceline, and how Marceline's guarded heart could open up to Finn. Additionally, the fact that they come from different worlds, with Finn being a human and Marceline a vampire, adds an extra layer of intrigue to their potential relationship.
The plot is crucial. It shouldn't just be about the 'lemon' aspect. A good plot could involve Marceline's relationships, her past, or her adventures in the Land of Ooo. Maybe there's a mystery she has to solve, or a conflict with another character that adds depth to the story. And of course, the romantic or sexual elements, if done tastefully, can enhance the overall story.
One great Finn Marceline fanfic is 'The Adventure Beyond the Night'. It beautifully weaves their relationship, showing how Finn's courage and Marceline's mystery come together in a story full of adventure. Another one could be 'Finn and Marceline's Unusual Bond', which focuses on the development of their unique friendship and how it might turn into something more in a very heartwarming way. And 'Marceline's Influence on Finn' is also interesting, as it delves into how Marceline's presence affects Finn's growth and understanding of the world around him.
In the context of Adventure Time, Finn and Marceline having a romantic or sexual relationship in fanfiction can be a controversial topic. Adventure Time is a show aimed at a wide audience, including children. Such explicit content in fanfiction goes against the family - friendly nature of the original show. So, it is not appropriate in the sense that it strays far from the intended spirit of the series.