Another idea is a crossover with the Star Trek universe. The X - Men could find themselves on a Starfleet ship. They might have to deal with the differences in cultures and technologies while also trying to stop Apocalypse from spreading his chaos across the galaxy.
Gandalf from 'The Lord of the Rings'. His magic and wisdom could add a new dimension to the story. He could help the X - Men in their fight against Apocalypse, perhaps using his magic to counter some of Apocalypse's powers or providing strategic advice.
There might be a fanfiction where Ororo and Charles are caught in a time - travel anomaly. This forces them to rely on each other more than ever. Ororo's elemental powers and Charles' mental abilities work in tandem to get them out of the mess. It's a story full of adventure and their interactions are really interesting.
Cooperation is a frequent theme as well. Since crossovers usually involve different groups coming together, they have to learn to cooperate. In fanfictions where the X - Men cross with other powerful entities, they need to find common ground and work together despite their differences.
One idea could be exploring the backstories of the minor mutants more. For example, how did they discover their powers before the events of Apocalypse. Another could be a time - travel fanfic where a mutant goes back in time to stop Apocalypse from ever rising to power. Maybe also a fanfic about the mutants trying to adapt to a post - Apocalypse world and rebuilding society in a more mutant - friendly way.
In some fanfictions, the best moment is when Charles first discovers Ororo's true potential. He looks into her mind and sees the vast power she could wield. It's a moment of revelation and sets the stage for their relationship to develop further.
One of the best is 'Age of Apocalypse'. It completely reshaped the X - Men universe. In this story, Apocalypse rules and the X - Men face a much darker and more challenging world. Another great one is 'X - Men: Apocalypse' which shows the battle against the powerful Apocalypse in a more modern take on the X - Men mythology.
Magneto is often a popular choice. His complex character, with his past traumas and his struggle between good and evil, offers a lot of room for exploration in fanfiction. Then there's Jean Grey. Her powerful abilities and her internal battles make her an interesting character to write about. And of course, Apocalypse himself. His motives and his grand plans are fascinating to dig into in fanfiction.
Well, it could be about the characters from Glitchtale suddenly finding themselves in the X - Men universe. Maybe Frisk would be mistaken for a new mutant with their unique abilities. They'd have to learn to fit in with the X - Men while also trying to find a way back home. The X - Men, on the other hand, would be intrigued by the strange new arrivals and their different kind of magic - like powers.
It could be really exciting. Picture Naruto's ninja skills combined with the mutant powers in X - Men Evolution. Maybe Naruto could team up with Cyclops and use his Rasengan while Cyclops blasts enemies with his optic beam. They'd make a formidable duo against common foes.