Another idea is a fanfic where Dobby tries to start a house - elf fashion revolution. He makes all these outlandish outfits for the house - elves at Hogwarts, and they start parading around in bright colors and crazy patterns. The wizards and witches are completely baffled by this new trend among the house - elves.
One funny idea could be a story where the Marauders accidentally turn themselves into cats and have to deal with life in Hogwarts as felines. They'd be chasing mice instead of playing pranks on Snape for a while, and it would be hilarious to see them trying to communicate with the other students while being cats.
A great funny art idea for Harry Potter fanfiction would be to illustrate a story where Dumbledore decides to hold a talent show at Hogwarts. Draw Neville doing a really bad but hilarious magic act that goes completely wrong, like making his toad turn into a giant balloon toad that floats around the Great Hall. You could also create art for a fanfic where the portraits on the walls start gossiping about the students. Depict the Fat Lady and Sir Cadogan chatting and pointing at students as they pass by.
A fanfiction could focus on a group of Hogwarts students who encounter a Nundu while on an unauthorized adventure in the Forbidden Forest. They have to use their combined magic skills, including spells they've learned in Defense Against the Dark Arts, to fend off the Nundu and find their way back to the castle safely. This would be a great way to show the growth and teamwork of the students.
One idea could be that Supergirl, while on a mission in a different dimension, accidentally lands in the wizarding world of Harry Potter. She is initially confused by the magic there as it's different from her own powers. Harry and his friends are both in awe and a bit wary of her. They could team up to fight a common enemy that threatens both the wizarding world and the world Supergirl is from.
The humor in Harry Potter fanfiction can come from the fact that it allows for more creative liberties. Fans can explore different relationships between characters in a light - hearted manner. For example, they might write about Hermione trying to teach Snape how to dance, which would be both absurd and funny considering their personalities in the original story. Also, the use of magic in comical scenarios, like using a spell to make Dumbledore's beard change colors every time he sneezes, adds to the hilarity.
Another concept could be that Harry Potter discovers he has a connection to Magneto's mutant powers. This might happen during a strange encounter with a dark magic object that unlocks a latent power within him. He then has to learn how to control these new abilities while also dealing with the threats in his own wizarding world, and he might seek out Magneto for guidance in a secret meeting across the boundaries of their two worlds.
One idea could be a story where Harry Potter has to team up with the Patil twins for a special Hogwarts project. They might discover a hidden chamber together and have to solve various magical puzzles within it.
In a fanfiction, Harry could be transported to the Pokemon world while on a mission for the Order of the Phoenix. There, he learns about Pokemon battles and uses his magic in unique ways to train and battle with his Pokemon team. He might also find that some Pokemon have a natural affinity for magic, and together they form an unbeatable combination.
One idea could be that Tinkerbell finds her way into the wizarding world of Harry Potter. Maybe she gets accidentally transported there by some magical mishap. She could use her fairy magic in Hogwarts, like helping to repair broken objects in a more sparkly and unique way compared to the Reparo charm.
In a fanfiction, Foster could be a descendant of an ancient wizarding family with a connection to the Bifrost. Harry Potter, while on one of his adventures, stumbles upon Foster. Together, they embark on a journey to the Bifrost. Along the journey, they learn about the history of their respective families and how they are intertwined with the magic of the Bifrost. They also face challenges like dark wizards who want to control the power of the Bifrost for evil purposes.
Perhaps a story about an adult wizard who was cursed and turned into a unicorn animagus against his will. He then has to navigate the wizarding world in this new form, facing prejudice from some who don't understand his condition. Along the way, he meets Harry Potter and his friends, who help him find a way to break the curse.