Perhaps the OC is a new student at the Xavier Institute. They have a power that is related to empathy but in an extreme way. They can feel and influence the emotions of others deeply. This causes some of the X - Men to form strong bonds with the OC, creating a harem dynamic. The OC could then struggle with how to handle these relationships while also dealing with the typical X - Men threats.
Another plot could involve an OC from a different dimension. They arrive in the X - Men Evolution universe with a power that no one has seen before. This power makes them a target for some villains, but also catches the eye of several X - Men. As the OC tries to find a way back home, they develop close relationships with these characters, resulting in a harem - like situation where the OC has to navigate different personalities and feelings.
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.
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 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.
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 that the OC has a special power that attracts Natsu and the other harem members. For example, the OC can control a unique type of magic that is crucial in saving the world, and Natsu is drawn to her courage. Another plot could involve the OC being from a different dimension and Natsu has to help her adapt to his world while falling in love. And perhaps there could be a rival in the harem who tries to drive the OC away from Natsu.
One idea could be that the OC is a powerful ninja from a far - off land. She comes to Konoha and catches the attention of Naruto and his friends. As she gets to know them better, she forms unique bonds with each of them, leading to a harem - like situation. For example, she might train with Naruto and they share their dreams of becoming Hokage and protecting the village. With Sasuke, she could be someone who understands his pain and tries to bring him back to the light. And with others like Shikamaru, she might engage in strategic battles and discussions, slowly building relationships.
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.
One idea could be the OC having a unique power that attracts the various characters in the harem. For example, if the OC can manipulate time in a certain way, it could lead to some really interesting situations. Maybe they use this power to save a member of the harem from a dangerous situation, which then makes that character develop strong feelings for the OC. Another plot idea is the OC being from a different dimension and having to adapt to the Highschool DxD world while building relationships with the harem members.
One idea could be that the OC is a new fighter in the Mortal Kombat tournament. As they progress, they attract the attention of various characters from different realms who then form a harem around the OC. Maybe the OC has a unique power that intrigues them all.