Well, your OC could be a lost reploid from an ancient civilization. This OC might hold the key to a forgotten technology that could either save or destroy the world in the Mega Man X universe. They would have to navigate the politics and battles while trying to figure out their own origin and purpose. Also, an OC that was created by a villain but has a sense of good could be an interesting plot. This OC would constantly struggle between their programming and their new - found moral compass.
A great plot idea could be an OC that is an outcast reploid because they have a malfunction that gives them uncontrollable bursts of power. In the Mega Man X fanfiction, this OC could be on a journey to find a way to control their power and in the process, they meet X and Zero. They could initially be seen as a threat but as the story progresses, they become an important ally. The OC could also have a unique design that reflects their outcast status, like having parts that are different from the standard reploid design.
One idea could be that Mega Man X and Nana team up to face a new, powerful enemy that neither could defeat alone. They have to combine their unique skills, like X's combat abilities and Nana's support functions.
One idea could be a story where Bass has to team up with Mega Man X to face a new, extremely powerful enemy that neither could defeat alone. Maybe this enemy has the ability to corrupt the reploid's programming, forcing them to work together to find a cure as well as stop the threat.
One idea could be a crossover with the Sonic universe. Mega Man X and Sonic could team up to stop a new villain that is causing chaos in both their worlds. This would involve X's advanced weaponry and Sonic's speed working together in a high - action adventure.
One possible plot idea could be that Rock and X team up to face a new and powerful enemy that neither could defeat alone. For example, a super - advanced robot created by a long - lost mad scientist.
A really interesting Mega Man X fan fiction plot could be centered around a new type of Maverick that is immune to X's normal attacks. X has to go on a journey to find a way to upgrade his weaponry and adapt to this new threat. Along the way, he meets an old ally who has been in hiding and has some crucial information. Another plot could involve X being sent on a mission to a far - off planet where the Maverick virus has taken on a completely different form. He has to learn the ways of this new world to defeat the Mavericks there. And for the third one, we could have a story where X accidentally activates an ancient defense system that starts attacking both humans and Mavericks, and he has to find a way to shut it down.
One idea could be that Mega Man X and Quake Woman team up to face a new powerful enemy that is causing earthquakes all over the world. They have to combine their skills, with X's speed and combat abilities and Quake Woman's power over seismic activity to defeat the foe.
Well, a plot could revolve around a young inventor in a parallel universe who discovers a way to communicate with the original Mega Man. Together, they try to find a solution to a virus that is spreading across multiple Mega Man universes, corrupting all the robotic beings. This would involve lots of action, as they have to fight their way through hordes of corrupted robots while also searching for a cure.
Well, a great plot for a Running Man x OC fanfiction could be that the OC is a world - class athlete who comes to the show to prove that they are the best. Along the way, they form friendships and rivalries with the regular Running Man cast. Or perhaps the OC is an alien who crash - lands near the set of Running Man and is forced to participate in the games to earn their way back home. Also, the OC could be a detective who is investigating a mystery related to the Running Man show and has to join the games to gather clues.
One idea could be Mega Man traveling back in time to stop Dr. Wily from ever starting his evil plans. He could meet a younger version of Dr. Light and work together to prevent the future disasters. Another plot could be Mega Man accidentally traveling to a post - apocalyptic future where his actions in the past led to a world ruled by machines. He then has to go back and change things.
One plot idea could be that the Spider Man OC and Felica team up to take on a new villain in the city. This villain could have a power that is specifically designed to counter both of their abilities, forcing them to work closely together and develop new skills. Another idea is that Felica discovers the identity of the Spider Man OC by accident, and this knowledge creates a whole new dynamic between them, with trust and secrecy being major themes.