You could do a crossover with the Inhumans. The X Men and Inhumans have some similarities in terms of having special abilities. In the fanfiction, there could be a misunderstanding at first between the two groups. For example, Beast could be fascinated by the Inhuman biology while some of the more hot - headed X Men like Gambit might be a bit more aggressive in their initial interactions. Then they would have to work together to face a threat like an alien invasion.
One idea could be creating an OC with a unique mutation that has never been seen before in the X - Men universe. For example, the ability to manipulate time on a small scale, like slowing down or speeding up time in a limited area. This OC could be a new student at the Xavier Institute and face challenges in controlling their power while also trying to fit in with the other mutants.
There could be crossovers with other superhero universes. For example, a crossover with the Avengers might have the X - Men teaming up with Iron Man and Captain America to fight a common enemy. It could also feature different versions of the X - Men characters, like a darker take on Wolverine.
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.
A genetic experiment gone wrong could also be a great plot for the crossover. A mad scientist tries to combine mutant and super - soldier DNA. This creates a new breed of dangerous creatures. The X - Men, with their knowledge of mutants, and the Avengers, with their combat skills and high - tech resources, must work together to contain the threat. Jean Grey's telepathic powers could be crucial in finding the source of the experiment, while Iron Man uses his technology to develop a way to reverse the genetic changes.
The OC could be a mutant from a different country who comes to the X - Men school. Pietro is immediately intrigued by her different culture and way of using her powers. They start to exchange stories about their mutant experiences, and a relationship forms based on mutual understanding and respect for their differences.
One possible plot could be that Sasuke, through some sort of interdimensional rift, ends up in the X - Men Evolution universe. He might initially be seen as a threat due to his powers and brooding nature. But then, he could team up with the X - Men to fight a common enemy, like a powerful mutant who wants to use Sasuke's Sharingan for evil purposes. Along the way, Sasuke could learn about the concept of mutants and their struggle for acceptance, which might change his own views on power and belonging.
One plot idea could be that the OC is a new mutant at the school and Kurt is assigned to show them around. They start off as friends but gradually develop deeper feelings as they face challenges together, like dealing with a bully mutant. Another could be the OC has a special power that Kurt needs to help control, and in the process, they bond over their shared experiences of being different.
One idea could be an OC who has the power to manipulate time and uses it to prevent a major disaster in the X - Men Evolution universe. Maybe they go back in time to stop a powerful mutant from turning evil and causing chaos.
One idea could be an OC with a unique power that attracts the attention of multiple X - Men characters, leading to a harem - like situation. For example, an OC who can manipulate time on a small scale. This power could be both useful and dangerous, and different X - Men might have different reactions to it, some being intrigued and others being cautious.
One idea could be inserting yourself as a new mutant with a unique power that the X - Men initially suspect but then come to trust. For example, a power to manipulate time on a small scale, which could be used to save the team from a sudden ambush.