First, choose the characters from both universes carefully. Decide which ones will interact and how. For example, you could start with Bakugo from My Hero Academia ending up in New York City from the Marvel universe. Then, create a conflict. Maybe a villain from Marvel, like Loki, is causing trouble and Bakugo's explosive quirk can be both a problem and a solution in this new world. Don't forget to add some character development. Bakugo could learn about teamwork from the Avengers, which is something he struggles with in his own world.
Well, it could be amazing. Picture Deku from My Hero Academia suddenly in the Marvel universe. He might be confused at first but then start to adapt. He could meet Spider - Man and learn new ways of using his quirk. Maybe they'd team up to fight a common villain like Doctor Octopus who has somehow made his way into the My Hero Academia world too. There are so many possibilities for crossovers between the unique powers in My Hero Academia and the well - known heroes and villains of Marvel.
Another great story could involve All Might and Captain America. Picture them meeting and sharing their ideals about heroism. They could train together and exchange combat techniques. Then, they face a threat that requires both their strength and leadership. For example, a new super - villain that has the powers of both the quirks from My Hero Academia and the super - powers from Marvel.
Doctor Strange with a Quirk like Eri's Rewind. He could not only manipulate time and space with his magic but also use the Rewind Quirk to reverse damage or even reverse the actions of enemies. This combination would make him a very versatile and powerful character, able to heal allies and counterattack enemies in ways that would be very difficult to defend against.
One great 'My Hero Academia' crossover fanfiction is the one where they cross over with 'One Piece'. It combines the unique powers of the 'My Hero Academia' world with the adventurous and diverse world of 'One Piece'. The characters interact in really interesting ways, like Midoriya being amazed by Luffy's Devil Fruit powers and Luffy being intrigued by the concept of Quirks.
Momo Yaoyorozu and Tony Stark. Momo has the ability to create any non - living object she can think of as long as she knows its molecular structure. Tony Stark is a genius inventor. They could collaborate on creating amazing new gadgets and weapons. Momo could provide the raw materials with her quirk, and Stark could use his engineering skills to put them together. It would be a combination of brains and super - powers that could create some really unique and powerful items for the heroes.
Here's a simple start for a 'prototype My Hero Academia crossover fanfic': In a world where the quirks of My Hero Academia exist alongside the powers from 'prototype'. Alex Mercer finds himself in the middle of Musutafu city. He's confused by the sight of people with all these strange abilities. Izuku Midoriya spots this strange man and approaches him. Mercer, being the shape - shifter he is, tries to blend in but his lack of knowledge about quirks starts causing some misunderstandings. As they interact, Mercer realizes that these 'quirks' could be a new form of power to study, while Midoriya is both fascinated and a bit scared of Mercer's abilities.
One idea could be that Kakashi is somehow transported to the My Hero Academia world. He could become a teacher at UA, using his ninja skills and wisdom to train the students in new and unique ways. His Sharingan would be a very interesting power in the MHA universe.
A common theme is the exploration of power. Since both universes have characters with unique abilities, fanfictions often delve into how these powers are used, abused, or developed further.
A great crossover idea is with the Dragon Ball series. The powerful Saiyans could interact with the My Hero Academia characters. Goku could train the students at UA to reach new levels of power. Also, a crossover with the Attack on Titan world would be intense. The heroes would have to deal with Titans in a whole new way and use their quirks in that battle - filled environment.