Maybe a spell goes wrong and causes a character to develop diabetes. The story could then be about how they adapt to this new situation. They might search for a magical cure within the wizarding world, or learn to live with it with the help of their friends, like Hermione using her research skills to find suitable magical remedies or ways to manage it.
Maybe Harry discovers a hidden part of Hogwarts where a Wendigo has been lurking. He has to use his magic skills to either defeat it or find a way to coexist with it.
Perhaps in a 'harry potter yells fanfiction', Harry yells when he discovers that someone has been spreading false rumors about his friends. He could be in the Great Hall, stand up, and yell at the perpetrator, creating a big scene full of drama and conflict within Hogwarts.
One way to find 'diabetic Harry Potter fanfiction' could be to reach out to the Harry Potter fan community on social media platforms. Post a request asking if anyone has read or written such fanfiction. This way, you might be able to get some leads from fans who are more in - the - know about this particular type of fan - created story.
One plot idea could be that Tony Stark somehow travels to the wizarding world. He could use his technological knowledge to improve the wizarding devices. For example, he might make brooms fly faster with some kind of engine modification.
Well, one plot idea could be that Harry discovers he has a special gift for breeding magical animals that no one else has. He starts breeding rare and endangered magical creatures secretly in the Forbidden Forest. Eventually, his activities are discovered, but instead of getting in trouble, he is asked to help save the magical animal population in the wizarding world.
One plot idea could be that Harry discovers his new 'God of Mischief' status and uses it to outwit Voldemort in unexpected ways. For example, he could create illusions that drive Voldemort's followers crazy or play tricks on Death Eaters during battles.
One plot idea could be that Henrik Mikaelson somehow gets transported into the 'Harry Potter' universe. Maybe he has his vampire powers and has to hide them among the wizards. He could form an unlikely friendship with Harry and help him in his battles using his unique abilities.
One plot idea could be that Haley Jones is a transfer student from a different magical school to Hogwarts. She could bring with her some unique magical abilities or knowledge that intrigues Harry and his friends. For example, she might know a different type of magic related to time - travel that could help in solving some of the mysteries in the Harry Potter world.
Perhaps Harry discovers he's a shapeshifter early on in his Hogwarts years. He might use this power to play pranks on the Slytherins by changing into a mouse and scaring them in the dungeons. But then, he realizes he has a greater responsibility when he sees the potential of using it against the Dark Arts. For example, he could shift into a large and powerful animal like a hippogriff to fight off Dementors.
One main plot idea could be Harry using his new - found lordly power to reform the wizarding world. He might change the laws regarding house - elves, for example. Another could be him facing off against new, more powerful dark forces that are threatened by his power and status.