One interesting 'Harry Potter Disney fanfic' could be about Harry Potter and his friends visiting Disneyland. Maybe they get lost in the Magic Kingdom and have to use their magic skills to find their way back. It would be a fun adventure with a mix of the two magical worlds.
There are 'Harry Potter fanfic fanfic' that focus on time - travel scenarios. Imagine if a character from the later books travels back in time to the first year at Hogwarts. This can create a lot of interesting plot twists as they try to change or preserve the original story line. Also, some fanfic fanfic might center around magical creatures in a way that wasn't fully explored in the original books, like the life of a hippogriff in more detail.
One idea could be that the Hogwarts students take a field trip to Disneyland. They could be amazed by the magical rides and meet Disney characters. For example, Hermione might be fascinated by the technology behind the rides and try to figure out how they work while Harry and Ron are more interested in the food. Another idea is that Disney villains team up with Voldemort. The Evil Queen could use her magic mirror to help Voldemort find Harry Potter. And Maleficent could use her dark powers to assist in the battles at Hogwarts.
Some 'Harry Potter and Lily Potter fanfic' might focus on alternate universes. In one such story, Lily could have survived Voldemort's attack. She would then have to raise Harry in a world that is still recovering from the Dark Lord's first rise. This would change a lot of the dynamics in the story. Harry would grow up with his mother's love and protection, and Lily would have to deal with the knowledge that Voldemort could return at any time.
I'm not really in favor of the 'slaves' concept in fanfic as it can be a bit disturbing and against the positive spirit of the original 'Harry Potter' series. However, some fanfics might explore power dynamics in a more metaphorical way. But overall, the official 'Harry Potter' works focus on friendship, courage and magic, not slavery themes.
One interesting 'Harry Potter breed fanfic' story could be about the breeding of Hippogriffs in a more domesticated setting. Maybe it explores how wizards are trying to train them for various tasks like mail delivery in a different way than using owls.
One interesting 'Harry Potter Siren Fanfic' could be about a siren who uses her charm to influence the events at Hogwarts in a subtle way. Maybe she befriends Harry and tries to guide him through some challenges using her siren - like powers, which are different from magic but still effective.
There might be a fanfic where a MACUSA auror teams up with a Hogwarts student. They could be working together to stop a dark wizard who is causing chaos in both the American and British wizarding worlds. The story could explore how their different magical educations and approaches to magic come into play.
One interesting 'Harry Potter glutton fanfic' could be about Harry discovering a magical kitchen that creates endless amounts of his favorite wizarding treats. He goes on a bit of a food - filled adventure, trying all sorts of new and old magical delicacies.
There could be a 'Harry Potter betrothed fanfic' where Harry is betrothed to a new character created by the author. This new character might be from a different magical family. The story could then revolve around Harry learning about this new family's traditions and trying to blend them with his own life at Hogwarts.
Well, in many Harry Potter fanfics about the girls, Hermione is often depicted in various new adventures. For example, she might go on a solo mission to discover a long - lost magic spell. Another could be Ginny's story where she becomes a leading figure in a new Quidditch league.