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.
In a fanfiction, they could exist if Wolverine was a sort of mentor figure. He could teach the young heroes in My Hero Academia about his combat style, which is very different from what they're used to. His no - nonsense approach and his experience could be valuable assets for the students at UA. Also, his adamantium claws would be a unique weapon in the world of MHA, and seeing how he uses them against the various villains with different Quirks would be exciting.
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.
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.
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.
Well, Wolverine could fit into the My Hero Academia storyline as a foreign hero or a special guest. His mutant powers would be seen as a very unique form of 'quirk' in the MHA world. He could be brought in to train the students at UA, sharing his combat experience which is far different from what they usually get. Maybe he could be part of a special international hero exchange program.
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 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.
A plot could revolve around Wolverine being sent to the My Hero Academia world to hunt down a mutant - like being that has escaped into this universe. However, he quickly realizes that the world has its own set of rules and heroes. He teams up with Midoriya and the others to find this being. Along the way, he teaches them about survival and the harsher side of combat, which is different from what they learn at UA. And in the end, they all learn from each other and Wolverine has a newfound respect for the young heroes.
The Infinity Gauntlet would likely cause chaos. In My Hero Academia, society is built around the concept of Quirks and how they are used. If the Infinity Gauntlet entered this world, it would introduce a new form of power that is not based on genetics but on an external, extremely powerful object. This would disrupt the existing balance between heroes and villains. Villains might see it as a way to finally achieve their goals of domination, while heroes would have to figure out how to deal with a power that is far beyond what they are used to facing.
It can also expand the universe in terms of relationships. When Deku fuses with other characters, it can lead to different interactions with his friends, family, and teachers. For instance, his friends might be initially hesitant or overly excited about his new fused quirk, which can create various story arcs. Moreover, the fanfiction could explore how the fused quirk affects Deku's standing in the hero community, whether he is seen as more of a threat or a greater hope.
Gohan could fit in by being a transfer student. His Saiyan powers would be seen as a very unique 'quirk'. In the harem aspect, his kind heart would draw the attention of the female characters. For example, Mina would find his positive attitude infectious.