The male OC could be a hacker who gets involved in a conspiracy in Gotham. He accidentally uncovers a plot by a powerful group to take over the city's infrastructure. He has to use his hacking skills to stop them while also avoiding being caught by the group's enforcers. Another plot idea is that he's a bartender who overhears a lot of criminal plans. He starts to pass on the information to the police, but soon the criminals figure out that he's the leak. So he has to go on the run and also find a way to bring the criminals to justice. Or the male OC could be an artist who uses his art as a form of protest against the crime and decay in Gotham. His art starts to gain a following and becomes a symbol of resistance, which angers the criminals who then target him.
A great plot could be that the male OC is a street magician in Gotham. One day, he discovers that his magic tricks are actually real magic due to an ancient artifact he found. He then uses this magic to fight crime, but he has to keep it a secret from the authorities and the criminal underworld. Or perhaps the male OC is a detective who has a unique ability to see the memories of the dead. This helps him solve crimes that no one else can, but it also takes a toll on his mental health as he is constantly exposed to the trauma of the victims. Another plot could be that he's a young heir to a wealthy family who decides to use his family's resources to fight against the poverty and crime in Gotham instead of living a life of luxury.
A great plot for Gotham Academy fanfiction could be a story centered around a school competition that turns out to be rigged. The main characters suspect foul play and start their own investigation. Or perhaps a story where a character from a villain's family enrolls at the academy and has to deal with the prejudice from other students while also trying to prove they're not like their family. Also, a plot about a haunted dormitory at Gotham Academy would be really cool. The students would have to figure out the mystery behind the hauntings.
Perhaps there's a villain in Gotham who has discovered a way to siphon the Flash's speed force. The Flash has to go to Gotham to stop this villain, and in the process, he meets the various characters of Gotham like Gordon and Catwoman. They all have to work together to not only stop the villain from stealing the speed force but also from using it for some evil plan in Gotham.
Maybe there's a meta - human or a super - villain who is causing chaos in both cities. Batman is too occupied with Gotham's internal affairs, so Arrow comes to help. They discover that the villain has a base in an abandoned area between the two cities. They have to combine their resources, like Arrow's high - tech arrows and Batman's detective skills (even if Batman himself isn't directly involved but his influence on Gotham's crime - fighting is there), to take down the bad guy.
One idea could be Marinette moving to Gotham and using her unique skills to help the city in a different way than the local heroes. For example, she could use her fashion design skills to create protective gear for the people in dangerous areas. Another plot could involve her befriending some of the Gotham characters like Barbara Gordon and sharing her positive outlook, which gradually changes the gloomy atmosphere of Gotham. She might also get involved in some of the city's mysteries and use her cleverness to solve them.
One idea could be that the male reader is a scientist who is trying to find a cure for Mister Freeze's condition. As they work together, a deep bond forms between them. Maybe the reader gets into trouble with other villains in Gotham because of his association with Mister Freeze, and Mister Freeze has to protect him.
Well, a plot could be that the male OC is a time - traveler. He arrives in Camelot during Merlin's time and has knowledge of future events. This causes a stir as Merlin tries to figure out if he can trust this stranger. Maybe the OC is from a future where magic has been fully accepted and he tries to bring that ideology to Camelot. Or perhaps the male OC is an artist who uses magic in his art, and his works start to have strange effects on the people of Camelot, leading Merlin to investigate.
One idea could be a male oc who is a new student in Riverdale. He has a mysterious past related to a big city crime syndicate. As he tries to fit in at Riverdale High, he gets involved with the core group of friends. Maybe he has some special skills like being an expert in martial arts or a whiz at hacking, which he uses to help solve the town's mysteries. Another plot could be that he is an aspiring musician who gets caught up in the drama between the music clubs at school and the local music scene in Riverdale. He could also have a romantic sub - plot with one of the female characters, like Betty or Veronica, but there are obstacles in their relationship due to his secrets.
A plot could involve the male OC being a long - lost relative of one of Artemis' allies. He shows up unexpectedly and has a mysterious past. Artemis is initially suspicious of him but as they work together to solve a series of strange disappearances in the forest, she begins to trust him. They discover that an ancient evil is behind the disappearances and must combine their skills to defeat it. Maybe the male OC has some knowledge of ancient magic that Artemis needs to learn.
One idea could be that the male OC with the Omnitrix accidentally gets transported to an alternate dimension where the Omnitrix functions differently. He has to figure out how to adapt and use it to get back home. Another plot could involve the OC using the Omnitrix to stop an alien invasion that is targeting his hometown specifically. Maybe the aliens are after the Omnitrix's power source.
A great plot could involve the Dark Knights having to team up with some of Gotham's most unlikely allies, such as former villains who have turned over a new leaf. They could be brought together by a common threat that is too big for any of them to handle alone. Also, a plot where the Dark Knights discover a long - hidden secret about Gotham's founding that has the potential to change everything they know about the city and their role in it.