Fanfiction ideas combining Phantom of the Opera and The Little Mermaid

One idea could be that Marinette (from Miraculous Ladybug) discovers a magical seashell that transports her to the underwater world of The Little Mermaid. There, she meets Ariel and they team up to fight an underwater villain who is stealing the magic of both the surface and the seabed. Maybe the villain is after the Miraculous and Ariel's voice for some dark purpose.

A more complex fanfiction could be about Starfire getting stuck in Danny's world. She has to adapt to living in a world where ghosts exist and not everyone is as friendly as in her own. Danny helps her understand the rules of his world, and in the process, they develop a strong friendship that could potentially turn into something more romantic as the story progresses.

A fanfiction could also explore a scenario where Peter Parker gets some ghostly powers similar to Danny's due to an experiment gone wrong. He then has to learn how to control these new powers while still being Spiderman. Danny could come to help him understand and master these powers.

One idea could be that the Joker somehow finds his way into the Danny Phantom universe. Maybe he teams up with one of Danny's villains, like Vlad, thinking they can cause more chaos together. They could plan to use Danny's ghost powers for some really wild and dangerous stunts across both the human and ghost worlds.

Imagine a fanfiction where the carnival in Italy is a backdrop for a magical encounter between the Phantom and Christine. The carnival has a traveling opera troupe performing 'The Phantom of the Opera' as part of its attractions. Christine is drawn to the performance and somehow, the Phantom is able to manifest himself within the fictional performance on stage. They then have a series of interactions that blur the lines between reality and the fictional world of the opera within the carnival setting.

The Phantom could view the mermaids as ethereal beings with voices that are pure and untainted by the harshness of the human world. He might be envious yet inspired by them. Meanwhile, the mermaids could see the Phantom as a mysterious and somewhat frightening figure at first. But as they get to know his love for music, they might start to understand him.

A plot could involve Gustave getting caught in a power struggle within the opera house. The Phantom might use Gustave as a pawn to gain more control, while Gustave has to figure out how to free himself from this web of manipulation. He could also befriend some of the performers and together they try to expose the Phantom's true intentions.

One idea could be a crossover where Naruto somehow ends up in the world of 'My Bride is a Mermaid'. Maybe he's on a mission and a strange jutsu goes wrong, transporting him there. He could meet the mermaid characters and get involved in their underwater adventures while also trying to find a way back to his own world.

One idea could be that Danny Phantom accidentally crosses paths with the Grim Reaper. Maybe the Grim Reaper is after a ghost that Danny has befriended, and Danny has to convince the Grim Reaper that the ghost has a good reason to still be around. For example, the ghost could be helping Danny protect Amity Park from other more malevolent ghosts.

Another fanfiction concept is that a character from The Walking Dead dies and becomes a ghost like in Danny Phantom's world. Danny has to help this new ghost come to terms with their situation while also dealing with the zombie apocalypse around them. This could explore themes of death, acceptance, and survival all at once.