Well, consider an OC that has the power of illusion but on a much grander scale than any other mutant in the X - Men Evolution world. This OC could create entire cities or landscapes as illusions. The story could be about how the X - Men initially suspect this OC of being a villain because of the large - scale illusions they create. But as the story unfolds, they realize that the OC is actually trying to help them by using their illusions to deceive their enemies.
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 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.
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 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 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.
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.
Maybe an OC who has the power of telepathy but in a very unique way. Instead of just reading minds, they can project their thoughts into the dreams of others. This OC could be used to either help the X - Men by warning them of threats through their dreams or be a villain who uses it to plant false ideas in their heads. They could have a complex backstory about how they developed this power and why they choose to use it in the way they do.
One idea could be an OC with the power to manipulate time. They could be a new recruit to the X - Men and struggle with using their power responsibly. For example, they might accidentally send a teammate into a different time period and have to figure out how to bring them back.
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.
A plot idea could be that Bobby and Jubilee get trapped in a time - loop. Each time they relive the day, they notice different things about each other and their powers. At first, they're frustrated, but as they work together to break the loop, they develop a deeper understanding of one another.
A popular one is 'X Men Evolution: The OC's Secret'. In this story, the OC has a secret past that slowly unfolds throughout the plot. The interactions between the OC and characters like Wolverine and Professor Xavier are really engaging. It keeps you hooked as you try to figure out what the OC's real motives and background are.