Maybe Princess Bubblegum creates a love potion to make Marceline fall in love with her, but things go wrong and it makes all the Candy Kingdom citizens fall in love with each other in a chaotic way. This could lead to a lot of humorous and heart - warming moments as they all try to sort out their new feelings.
A love potion could be discovered in an old dungeon. When Peppermint Butler gets his hands on it, he uses it on himself to fall in love with the idea of power. Then he starts causing trouble in the Land of Ooo as he tries to gain more power for his 'love'. Finn and Jake then have to stop him while also dealing with the side - effects of the potion.
One idea could be a student accidentally using a love potion on a teacher, creating chaos in Hogwarts. For example, if a first - year student manages to get their hands on a love potion and uses it on Professor Snape, who then starts acting completely out of character, being overly friendly and kind, which confuses all the students.
Well, a possible plot idea for 'a bittersweet potion fanfic' is that the potion is created by an inexperienced wizard. The wizard doesn't realize that the potion has the power to make people experience their greatest fears and joys simultaneously. As the story unfolds, different characters drink the potion accidentally, and we see how they deal with these intense and conflicting emotions. It could also be that the potion was meant for a noble purpose, like curing a plague, but has some bittersweet consequences like changing the appearance of those who take it.
One idea could be that Breezy gets lost in the Land of Ooo and Finn and Jake have to help her find her way back home. Maybe she has a special mission that she needs to complete but can't without their help.
One possible plot idea could be that a love potion is accidentally consumed by Sasuke, leading to some comical and confusing situations as he tries to deal with his new - found feelings for Naruto. For example, he might find himself blushing around Naruto all the time and doing things out of character to be close to him.
You could write a fanfic about how the Mushroom War affected the magical elements in the Adventure Time world. Maybe the war disrupted the balance of magic, and certain characters are on a quest to restore it. They might encounter strange new magical creatures or phenomena that were born out of the chaos of the war.
One plot idea could be that Finn and Jake from Adventure Time end up in the Fallout wasteland. Finn, with his sword skills, could be on a quest to find a special artifact to get back to their own world. Jake, with his shape - shifting abilities, might help them survive against the various mutated creatures in the Fallout universe. Another idea is that the Vault - Tec technology in Fallout somehow merges with the magical elements of Adventure Time, creating strange new hybrids of mutants and magical beings.
One idea could be Finn and Jake swapping bodies. Finn in Jake's body might struggle with Jake's more laid - back and sometimes lazy attitude towards things like guarding the Tree Fort. He could be shocked at how comfortable Jake is just lying around. Another plot could involve Princess Bubblegum and Marceline swapping. Princess Bubblegum, in Marceline's body, has to deal with Marceline's vampire instincts like craving blood (in a non - too - gory way, of course). This could lead to some comical situations as she tries to resist her new urges while Marceline, in Princess Bubblegum's body, has to handle the responsibilities of ruling the Candy Kingdom and might be a bit too carefree for the Candy People's liking.
One idea could be that the Water Princess discovers a hidden underwater kingdom that was once part of her domain but has been lost. Another could be her facing a drought in the Land of Ooo and having to use her powers in new and creative ways to bring water back. Maybe she has to team up with Finn and Jake to fight an enemy that is polluting the water sources.
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, perhaps in the 'Harry Potter spanking potion fanfic', there is a plot where a new potion master creates this spanking potion as an experiment. The students are curious about it and one of them, like Ron, accidentally drinks it and starts acting in a very strange way that involves involuntary spanking motions. This could lead to a series of hilarious events as his friends try to find a cure. Also, it could be that a dark wizard wants to use this potion to embarrass and control the Hogwarts students, which then leads to a battle of wits between the good guys and the bad guy.