Maybe a character from another dimension with Sharingan enters the My Hero Academia world. This character could then start sharing their knowledge and power with some of the local characters, like All Might's successor. This would change the power dynamics in the story.
It can be integrated through a magical artifact. For instance, a mysterious relic is discovered in the My Hero Academia world that bestows the Sharingan upon those who touch it. This could lead to a race among heroes and villains to obtain it.
In fanfiction, the Sharingan could be the result of a scientific experiment gone wrong. A scientist in the My Hero Academia world could be trying to create a new quirk - enhancing device but instead ends up giving a character the Sharingan ability. This would then cause a stir in the hero and villain communities as they try to figure out what this new power means and how to deal with it.
One way it could fit is by having a character with a quirk that allows them to mimic the Sharingan's abilities. For example, they might be able to copy other heroes' or villains' quirks in a similar way to how the Sharingan can copy jutsu in Naruto. This would add a whole new level of strategy and intrigue to the My Hero Academia world.
Well, one way could be to make her a new student at UA. She could have a unique quirk that sets her apart from the others, like the ability to manipulate light for various purposes, such as creating illusions or blinding enemies. This would make her an interesting addition to the story and give her a role in battles and training sessions.
Naruto's ability to make friends easily could also play a big role. He could form alliances with students at U.A. High School. His positive attitude would be a contrast to the dark shadow of his 'villain' father. For example, he could befriend Midoriya and they could learn from each other's experiences of growing up different from the norm.
In a fanfiction scenario, the Hulk might be a result of a secret experiment by the League of Villains to create an ultimate weapon. But instead of being fully controllable, he breaks free and becomes a wild card in the power dynamics of the My Hero Academia world. His presence would disrupt the existing balance between heroes and villains as everyone tries to either control or destroy him.
It could be integrated through a scientific experiment gone wrong. Maybe a mad scientist in the Boku no Hero Academia universe is trying to create a new type of power - up for heroes, but instead creates a Venom - like symbiote. This symbiote then starts to infect characters, changing their abilities and personalities. This can lead to all kinds of new storylines as the characters have to deal with these unexpected changes.
Goku could be seen as an alien with an extremely powerful 'Quirk' in the My Hero Academia world. His Saiyan abilities like flight, super strength, and energy blasts could be considered a new type of Quirk. He would likely stand out a lot and attract the attention of both heroes and villains.
In fanfiction, the Mangekyou Sharingan's unique abilities like Amaterasu (the black flames) could be combined with Fairy Tail's elemental magics. Imagine a character using Amaterasu - like flames in combination with fire - based Fairy Tail magic to create an even more powerful and destructive attack.
First, think about their Saiyan powers and how they would translate in the My Hero Academia world. For example, a Saiyan's ability to increase power level could be like a quirk that gets stronger over time. Consider their backstory, like maybe they're a Saiyan from another planet who ends up in the MHA world. Also, their appearance can combine Saiyan features like a tail and spiky hair with the MHA style of clothing.
One way they could exist in the same universe is through a crossover event. Maybe some sort of interdimensional rift brings Wolverine into the My Hero Academia world. His mutant powers would be quite different from the Quirks in MHA, which could lead to interesting interactions. For example, his healing factor might be seen as an extremely powerful Quirk, and heroes or villains in the MHA world could either be in awe of it or try to find a way to counter it.
A great fanfiction idea might be a crossover where characters from Naruto with Sharingan abilities are brought into the My Hero Academia world. They could teach the My Hero Academia characters about the power of the Sharingan and how to use it, leading to some really cool team - up battles and training sessions.