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.
In some fanfictions, there might be a crossover where the hero academies in both universes interact. Imagine U.A. High students visiting the school in Invincible's world. This could lead to interesting exchanges of training methods and ideas about heroism. Also, characters like All Might and Omni - Man could have some intense philosophical debates about power and responsibility.
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.
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.
The Powerpuff Girls. Blossom, Bubbles and Buttercup in the world of My Hero Academia would be amazing. They could team up with the female heroes like Uraraka and Tsuyu. Their superpowers could combine with the quirks in some really unique battles against powerful villains.
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.
One idea could be Batman getting transported to the My Hero Academia universe. He could team up with Izuku Midoriya and share his detective skills and combat expertise. Another could be a scenario where some of the My Hero Academia villains steal Batman's technology and the heroes have to work with Batman to get it back.
There could be a fanfic where the Quirks in My Hero Academia are seen as a form of Haki in the One Piece world. The heroes and villains from My Hero Academia have to adapt to this new way of seeing their powers. This creates a whole new set of challenges and alliances. For example, All Might could be seen as a Yonko - level threat with his powerful Quirk, which is now considered a super - strong form of Haki.
One popular trope is the 'Quirkless Hero' where a character without a quirk manages to become a hero through sheer determination and intelligence. Another is 'Villain Redemption', where a villain decides to change their ways. 'Time Travel' is also quite common, with characters going back in time to fix things in the My Hero Academia universe.
One idea could be a crossover with the Naruto universe. The characters from My Hero Academia could interact with Naruto characters. For example, Deku might learn some new fighting techniques from Naruto. Another idea is a crossover with the Harry Potter world. The students at U.A. could visit Hogwarts and experience magic, while the Hogwarts students could learn about quirks.
A cool My Hero Academia crossover fanfiction idea would be with the Avengers. The heroes from UA could team up with the Avengers to fight a common enemy. For example, a powerful villain who can absorb quirks and powers. It would be interesting to see how characters like All Might and Captain America interact, and how their leadership styles differ.