One idea is that there's a new spell in the Harry Potter universe that involves lemons and unicorns. Harry Potter could be the first to discover it while interacting with a unicorn. Maybe it's a spell that can transform things into lemon - flavored magical treats for a short time, and the unicorn is the key to unlocking this spell.
The fanfiction could center around a magical festival in the wizarding world. Unicorns are a big part of this festival, and lemons play a role in the traditional foods or decorations. Harry Potter gets involved in the festival preparations and has an adventure related to the unicorns and the lemons. He could learn about the ancient traditions and magic that bind these three elements together.
In 'harry potter is a demigod fanfiction', we could see a lot of changes to the existing story. For example, the magical world might have to interact with the world of the gods. There could be new enemies, like monsters from Greek or Roman mythology. Also, Harry's relationships with his friends and teachers might be different. His identity as a demigod could make him both more powerful and more of a target. He might have to go on quests like a typical demigod, which would be very different from his normal Hogwarts adventures.
It could entail a story about a Nundu being used in the Triwizard Tournament as an unexpected and extremely dangerous challenge. The champions would have to figure out a way to survive the encounter with the Nundu without using dark magic.
Well, it could be a story where Harry Potter discovers a unicorn in the Forbidden Forest and there's a 'lemon' moment, like a sweet, unexpected encounter. Maybe the unicorn has some magical power that's related to a lemon - like it can create lemon - scented magical auras or something.
It would be really wild. Maybe Harry Potter would have some of Ulquiorra's powers like his cero blast, but in the form of a wizard spell. Or perhaps he would have Ulquiorra's cold and emotionless demeanor in the wizarding world, which would be a huge contrast to his normal self. He could be dressed in a way that combines the Hogwarts robes with Ulquiorra's Arrancar outfit.
It would probably involve Harry Potter having Spartan - like abilities. Maybe he could be super strong and agile like a Spartan, while still being able to use magic. It could also include elements of the Halo universe, like the Covenant or the UNSC, interacting with the wizarding world.
The plot might involve Harry using his magic in an unorthodox way to summon Cthulhu. Maybe he stumbles upon an ancient spell in the restricted section of the library. Once summoned, Cthulhu could bring chaos to the wizarding world. The dark and eldritch powers of Cthulhu would be in stark contrast to the more traditional magic in Harry Potter. This could lead to a struggle between the forces of Hogwarts and the indescribable horror of Cthulhu.
The plot could involve Harry Potter being reborn in the Vampire Diaries universe with his magical abilities intact. He might face new challenges like dealing with vampires and witches in this different magical setting. Maybe he'd use his spells to protect himself from vampire attacks or form alliances with some of the characters. For example, he could team up with Bonnie Bennett, sharing magical knowledge. And he'd surely have to adapt to the different social structures and power dynamics in Mystic Falls.
Well, in unicorn lemon fanfiction, a common theme is the transformation theme. For example, the unicorn might transform things into lemon - based items using its magic. Also, there could be a theme of discovery where the unicorn discovers a hidden lemon grove in a magical realm and has all sorts of encounters there.
It might entail Queen Elizabeth as a character in the wizarding world. She could be a guest at Hogwarts, and all the students are curious about her. She might give a speech about leadership and how it's similar in the Muggle and wizarding worlds.
Perhaps a story about an adult wizard who was cursed and turned into a unicorn animagus against his will. He then has to navigate the wizarding world in this new form, facing prejudice from some who don't understand his condition. Along the way, he meets Harry Potter and his friends, who help him find a way to break the curse.