Yes, there might be some. Fanfiction websites like Archive of Our Own (AO3) could potentially have such fanfictions. However, the availability may vary. Some fanfic writers might explore this idea as a creative concept within the Adventure Time universe, but it's important to note that fanfiction is a form of fan - created content and not part of the official canon.
One great adventure time pregnant fanfiction could be one where Princess Bubblegum discovers she's pregnant and has to deal with the changes in her kingdom while also preparing for motherhood. It might explore how her scientific mind approaches pregnancy and how the other characters like Finn and Jake support her.
One possible plotline could be Marceline dealing with the challenges of pregnancy while still having to face the usual threats in the Land of Ooo. Maybe she has to rely on her friends like Finn and Jake more than ever for protection. Another could be exploring the relationship between her and the father of the baby, whoever that might be in the fanfiction, and how they navigate this new chapter in their lives.
To write an adventure time pregnant fanfiction, start with the character's emotions. If it's a character like Ice King, how would he feel if he found out his partner was pregnant? Then, build the world around the pregnancy. You can include elements from the show like the different lands and creatures. Also, don't forget about the relationships. How do the other characters interact with the pregnant one? It could be a story full of drama, humor, or both.
One possible adventure time pregnant fanfic could be about Princess Bubblegum becoming pregnant and how she manages her kingdom during that time. Maybe Finn and Jake would be there to support her in different ways.
The fanfiction could explore how Peter Parker and Amora first meet. Perhaps it's during a battle where Amora's magic and Peter's spider - powers cross paths. Then, as they get to know each other better, the pregnancy occurs. It would be a story full of emotion, as Peter has to grow up quickly and Amora has to adapt to the idea of having a child in a world she may not fully understand.
One possible scenario in this fanfiction could be that Belle discovers she is pregnant and has to deal with the complex relationship she has with Rumpelstiltskin. He might be initially shocked but then slowly come to terms with the idea of becoming a father. Their journey could involve him trying to protect her and the unborn child from the various threats in their fantastical world.
A possible plot could revolve around the baby's special abilities. Since Lady Rainicorn has her own set of abilities, it's likely the baby will inherit some. In the fanfiction, the characters could be speculating about what those abilities might be. And as the pregnancy progresses, there could be some signs or events that give hints about the baby's future powers. This could lead to a lot of anticipation and excitement among the characters.
There are many alternatives. For example, you can write fanfiction about the adventures of Finn and Jake in new, uncharted lands. Or perhaps create a story about Princess Bubblegum's latest scientific discovery. Another option could be to focus on the relationship between Marceline and Princess Bubblegum and how they interact in different situations.
First, know the characters well. For example, if you're writing about a pregnant Princess Bubblegum, remember her intelligence and leadership. Then, create a unique plot. Maybe there's a magical pregnancy or a situation where the baby has special powers. Also, add some humor like Adventure Time always has. For instance, Finn's reactions to the pregnancy can be really funny.