What are some interesting ideas for a Harry Potter Highlander crossover fanfiction?

Maybe a story where Harry Potter himself is revealed to be an Immortal. He would have to balance his fight against Voldemort with the rules of the Highlander's world. This could add a whole new layer of complexity to his journey. He might learn new combat skills from the Highlander lore and use them against Death Eaters.

One idea could be that Buffy and the Highlander team up to fight a common supernatural enemy that is causing chaos in both their worlds. Maybe a powerful demon that can't be killed easily, and the Highlander's immortality and Buffy's slayer skills are needed to defeat it.

One idea could be a Highlander character finding a Stargate and being transported to different planets. They could use their immortality to survive in the various dangerous situations on alien worlds and perhaps encounter Goa'uld who are interested in their immortality.

One idea could be that Xander discovers he has the immortality of a Highlander. He then has to navigate his newfound ability while still dealing with the usual supernatural threats in his world. Maybe he teams up with a Highlander character to learn more about his new condition.

Hermione Granger would be a great choice too. Her thirst for knowledge would lead her to study the lore of the Highlanders intensively. She could figure out ways to use magic to either protect Immortals or find a way to end the immortality curse if she saw it as a danger. Her intelligence would make her a force to be reckoned with in the Highlander's world.

A possible plot could involve an immortal villain from the Highlander world using the Stargate network to spread chaos across different planets. The SG1 team, with the help of some friendly Highlander characters, has to track him down and stop him before he causes too much destruction.

One idea could be that Merlin somehow gets transported to the Harry Potter universe. He could use his magic, which is different from the wizarding magic in Harry Potter, to solve some of the mysteries or problems there. Maybe he teams up with Harry and helps him defeat Voldemort in a unique way, like using his ancient magic knowledge.

One interesting idea could be a crossover with a fairytale world. For example, Hermione could be transported to a world like Cinderella's and meet a prince who has some magic similar to that in the Harry Potter universe. This would create a new kind of romantic dynamic where she has to balance her Hogwarts knowledge with this new, more traditional fairy - tale romance.

One idea could be that Hogwarts students discover Pokemon in the Forbidden Forest. They could start training them as part of a new magical - creature - handling class. Another idea is that a powerful Pokemon like Mewtwo ends up at Hogwarts and causes chaos among the students and teachers, who have to use their magic to deal with it. Also, a wizard could accidentally cast a spell on a Pokeball and create a new, hybrid Pokemon - magic creature.

In a Bleach and Harry Potter crossover fanfiction, it could be fascinating if the Quidditch players in Harry Potter had to face off against Hollows during a game. Imagine the chaos! Or perhaps the magic spells in Harry Potter could be used to enhance the powers of the Soul Reapers in Bleach. For example, a spell could be used to strengthen the bond between a Soul Reaper and their Zanpakuto. And if the Triwizard Tournament had a special task where the contestants had to team up with a Bleach character to defeat a powerful combined threat of a Dark wizard and a powerful Hollow.