Perhaps the catgirl is an emissary from a magical cat kingdom that has a connection to the Forbidden Forest. She comes to Hogwarts to seek help because the forest is being corrupted by a dark force. Harry and his friends join her on a journey into the forest to find the source of the corruption and cleanse it. Along the way, they discover new magical creatures and spells related to the catgirl's magical heritage.
Another idea is that the female vampire is actually an ancient protector of a powerful magical artifact. The artifact has been lost for centuries, and its location is somehow linked to Hogwarts. Harry Potter and his friends cross paths with the female vampire while on a quest to find the artifact. At first, they are wary of each other, but they soon realize that they need to work together. The vampire's unique abilities, such as enhanced senses and strength, help them in their search, and in return, Harry and his friends help her protect the artifact from those who would use it for evil.
A third idea could be a time - travel fanfiction. Imagine if a character, perhaps Hermione with her Time - Turner, accidentally travels back in time further than intended and has to figure out how to get back without disrupting the timeline too much. This could involve interactions with younger versions of the main characters or even the founders of Hogwarts.
One idea could be a story where Miss Martian attends Hogwarts as an exchange student. She has to learn how to adapt to the magical world, like using a wand and learning spells. Harry and his friends could help her with this. Another plot could be that a dark force from Miss Martian's world is threatening the wizarding world, and they have to team up to stop it. They could combine their unique powers, with Miss Martian's shape - shifting and telepathy and Harry's magic skills.
One idea could be that a centaur saves Harry from a dangerous creature in the Forbidden Forest and then they form a bond. The centaur could teach Harry about the ancient magic that the centaurs possess. Another plot could be a centaur acting as a guide for Harry during his search for a rare magical herb that only grows in centaur - protected areas. They would have to work together to overcome various obstacles.
One idea could be that a Succubus is a new kind of magical creature discovered in the Forbidden Forest. The Hogwarts students and professors have to figure out how to deal with it, whether it's a threat or not. Another could be a Succubus who has lost her powers and comes to Hogwarts seeking help to regain them in a non - sexual way, like learning about different kinds of magic.
One idea could be a story where the catgirl character is a new ninja in the Hidden Leaf Village. She has to learn the ways of the ninja from Naruto and his friends. For example, she could struggle with basic jutsu training, and Naruto helps her overcome her difficulties with his positive attitude. Another idea is that the catgirl is from a different clan that has a special connection to cats in the Naruto universe, and she teams up with Naruto to solve a mystery about a powerful cat - related artifact.
One idea could be exploring how Harry uses the experience of wearing girls' clothes to understand gender norms better in the wizarding world. Maybe he could use it as a disguise to get closer to certain secrets or people. It could also be a humorous take on how his friends react, like Ron being completely baffled at first.
How about a plot where the Polyjuice Potion is used in a school play? But things go wrong when the wrong ingredients are added, and the students start transforming into unexpected characters. They then have to figure out how to put on the play with their new identities while also trying to find a way to reverse the potion's effects before their parents and the whole school see them in this chaotic state. It would be a humorous and eventful fanfic idea.
One plot idea could be that Professor Sinistra discovers Harry has a natural aptitude for a rare form of Astronomy magic. She takes him under her wing to train him privately, and in the process, Harry uncovers a long - lost secret about Hogwarts' connection to the stars. This helps him in his fight against Voldemort later on.
There are indeed. Some non - adult fanfictions might have a catgirl character who is a part of an ancient magical cat - like race in the Harry Potter world. She could befriend the main characters and together they go on quests, learn new spells, or face off against dark wizards, all while maintaining a family - friendly and non - adult storyline.