Well, you could do a story where Jake's pups all grow up and have their own adventures. One of the pups could discover a time - traveling device and accidentally change the past in Ooo. This would lead to all sorts of chaos, like Finn not being found in the forest as a baby. Finn and Jake would then have to figure out how to set things right again.
One idea could be exploring the backstory of Marceline's mother. Maybe she was a powerful vampire from a different dimension and how that influenced Marceline's life. Another idea is a story where Finn and Jake discover a hidden land within Ooo that has its own unique set of magical creatures and rules. It could be a place filled with talking plants that are actually ancient sages.
A cool Adventure Time fan made story could revolve around Princess Bubblegum creating a new type of candy people who have special powers. But things go wrong when they start to rebel against her rule. Or perhaps a story about Ice King before he became the Ice King. He could have been a normal wizard who was cursed by an evil entity, and the story could be about his journey to break the curse.
One idea could be a fanfic where Finn and Jake discover a new, mysterious land full of strange creatures that have powers they've never seen before. Another could be a story about Princess Bubblegum's early days as a ruler, like how she built the Candy Kingdom from the ground up. Or perhaps a fanfic that focuses on Marceline's relationship with her father and how it affected her growth as a vampire.
Well, you could base your fan fiction on a 'what if' scenario. What if the adventure in 'Adventure of a Lifetime' took place in a post - apocalyptic world instead? The characters would have to face new challenges like mutated creatures and scarce resources. Or perhaps you could write a fan fic where the adventure is a dream within a dream. The main character thinks they've completed one adventure, but then wakes up to find they're still in another adventure that's even more dangerous and mysterious. You might also consider making the adventure a race against time to save a dying world, with the characters having to overcome not just physical obstacles but also moral dilemmas.
Well, in 'black clover fan made story', one interesting idea could be the new magical abilities created by fans. For example, a fan - made magic that combines elements in a unique way, like fire and water to create steam - based attacks. It shows the creativity of the fans.
One interesting idea could be the transformation of Finn into different magical creatures. For example, he could turn into a fire elemental, which would give him the ability to control and generate fire. This would completely change his fighting style and how he interacts with the Land of Ooo.
You could create a fanfic where Finn and Jake have to go on a mission to a completely new and unknown land in the Adventure Time world for your FRT fanfic. They might encounter strange new creatures and have to use their wits and powers in ways they haven't before. Maybe they find a land where the rules of magic are different, and they have to adapt quickly.
A great adventure time genderbend fanfic idea could involve Lumpy Space Princess as a male. He could be really vain in a different way, perhaps more focused on his muscles or some other masculine trait. And for Flame Princess, if she were a male, his relationship with Finn would be really different. Instead of the love - hate relationship they had, it could be more of a bromance, with them competing in feats of strength or something similar.
One idea could be a crossover with Steven Universe. Finn and Steven could team up to save both their worlds from a common threat. They both have a strong sense of justice and adventure, so it would be exciting to see them interact. Another could be a crossover with Gravity Falls. Dipper and Finn could go on a mystery - solving adventure together. The different magical elements of both shows would blend well.
One idea could be exploring Finn and Jake's further adventures in the Land of Ooo. Maybe they discover a new, hidden kingdom filled with strange creatures and magical artifacts. Another plot could revolve around Princess Bubblegum creating a new type of candy that has unexpected side effects on the inhabitants of the Candy Kingdom.
One idea could be a prequel focusing on the characters' lives before boarding the Poseidon. For example, showing how they got their tickets and what led them to be on that fateful journey.
One great adventure idea is to rent bikes and explore a new area. Maybe there are some old ruins or a beautiful lake to discover. You could also plan a mountain - climbing adventure with your friends. The feeling of reaching the peak together is amazing. And don't forget about going on a safari - like adventure in a large nature reserve. Spotting different animals and learning about their habitats would be really interesting.