A cool plot could be that a villain in the Boku no hero world steals Iron Man's technology and starts creating chaos. The heroes then have to figure out how to stop the villain while also dealing with the unfamiliar technology. Or perhaps a young inventor in the Boku no hero world idolizes Iron Man and tries to recreate his suits, but with a twist related to quirks. This could lead to a story about the young inventor's journey, from being an unknown to becoming a key figure in fighting crime with their unique Iron Man - inspired creations.
Maybe there's a plot where Iron Man's AI, like JARVIS or FRIDAY, gets integrated into the support system of the hero school in Boku no hero. This AI could then help in training the students, analyzing their quirks, and providing real - time advice during battles. It could also lead to some humorous situations where the AI doesn't quite understand the nuances of the quirk - based world at first, but over time becomes an invaluable asset.
It could be Midoriya. Imagine Midoriya getting access to Iron Man's technology. He's already a determined and intelligent hero - in - training, and with Iron Man's tech, he could become even more powerful. He might struggle at first to adapt to the new technology, but his strong will would drive him to master it and use it to protect others in new and exciting ways.
You could also write a fanfic about a time - travel plot. A character goes back in time to prevent a major disaster that happened in the 'boku no hero' world. They have to figure out how to change the past without completely disrupting the future, and along the way, they interact with younger versions of the beloved characters.
One idea could be a crossover with another popular superhero universe. For example, characters from 'Boku no Hero' could meet and team up with characters from the Marvel Universe. They could face a common enemy that requires both sets of powers to defeat. Another plot could involve a time - travel crossover, where a character from 'Boku no Hero' is sent to a different time period in another fictional world and has to adapt and find a way back. Or perhaps a crossover where the 'Boku no Hero' characters are transported to a post - apocalyptic world and must use their quirks to survive and help the locals.
One popular idea could be creating an alternate origin story for a character. For example, giving Deku a different quirk acquisition experience that still leads to his growth as a hero.
One idea could be exploring Stain's backstory in more detail. Maybe his early life experiences that led him to his extreme views. Another could be a 'what if' scenario where Stain teams up with a hero, albeit reluctantly, to take on a greater evil. And a third idea could be to write from the perspective of someone inspired by Stain's ideology but trying to find a more peaceful way to bring about change in the hero society.
One idea could be to combine the powers of the characters from 'Boku no Hero' with the epic battles and mythology of 'God of War'. For example, Deku could find a magical weapon from the 'God of War' universe that enhances his One For All power. Another idea is to have Kratos end up in the 'Boku no Hero' world and his combat skills and Spartan rage could make him a formidable hero or a feared villain. Or perhaps the Titans from 'God of War' could invade the world of 'Boku no Hero' and the heroes have to figure out how to stop them using their quirks.
One idea could be a fusion between Deku and All Might. Imagine Deku having not just One For All, but also All Might's combat experience and charisma from the start. It would change the dynamic of his battles and his relationships with other characters. Another idea is fusing Todoroki with a water - based hero, which could enhance his ice and water abilities even more and lead to new and creative ways of using his quirk in combat and rescue situations.
One idea could be to have the heroes and villains participate in a Halloween-themed battle royale. The setting could be a spooky, abandoned city filled with Halloween decorations. Another idea is to have a Halloween party at UA High School where students dress up as different heroes or villains from history. They could then have a contest for the best costume.
An interesting concept for a 'boku no hero academia oc fanfic' is an OC who is a villain at first but then slowly realizes the error of their ways. Their quirk could be something that is initially seen as very menacing, like the power to steal the quirks of others temporarily. As the story progresses, they could start using this quirk for good, like helping heroes regain their lost quirks in battles against stronger villains.
One idea could be creating a fanfic where a new student with a unique quirk joins U.A. High School. This new character could have a quirk that is both a blessing and a curse, like the ability to control time but at the cost of their own health. Another idea is to write a story about the villains' backstories in more detail. Maybe explore how they became villains and what events led them to oppose the heroes.