Ochaco Uraraka would likely find the fanfiction really fun. She has a bubbly personality and would enjoy reading about different anime worlds colliding or different versions of her favorite characters. She might even daydream about meeting some of the characters from the fanfiction in her own MHA world and having adventures with them.
Bakugo Katsuki, on the other hand, might be more dismissive at first. He'd think it's all just some made - up nonsense that has nothing to do with real hero work. But if he found a fanfiction that had an interesting battle scenario or a strong - willed character, he might grudgingly admit it had some merit. He'd probably scoff at any overly emotional or sappy parts though.
Some MHA characters might be really intrigued by Disney fanfiction. For example, Izuku Midoriya would probably be super excited. He loves stories and analyzing different characters' motives, just like he does with heroes. He'd be all about exploring the new worlds and character relationships in the Disney fanfics.
The MHA characters' reactions could vary widely. For instance, All Might might see the Naruto fanfiction as a great source of inspiration. He could admire the way the characters in Naruto strive for their goals, just like heroes in their own world. Todoroki might be a bit detached but still interested. He'd analyze how the power systems in Naruto compare to quirks in their world. Mineta would probably be more interested in any fan service - like elements if there were any, but that's not a very positive reaction. Overall, it really depends on each character's personality.
Some MHA characters might be really intrigued. For example, Izuku would probably study the magic systems in Fairy Tail fanfiction with great enthusiasm, seeing it as a new form of 'quirks' in a way. He'd be taking notes and trying to understand how the characters use their magic powers for good.
Midoriya Izuku could also have an interesting reaction. He's always trying to understand the villains better, and Dabi is a very mysterious villain. He might study the fanfictions to look for clues or insights into Dabi's character that he could use in a potential confrontation or in his quest to become a better hero. He might be surprised by some of the creative interpretations in the fanfictions.
I think All Might's reaction would be interesting. He might see Loid as a kind of hero in a different sense. Loid's selfless dedication to his mission to prevent war, even if it means living a double life, could remind All Might of his own role as a symbol of peace. All Might would probably respect Loid's determination.
I think Midoriya's reaction would be the most interesting. He's such a huge hero fan and analyst. He'd dissect every aspect of Batman in the fanfiction, from his combat skills to his psychological state. He might even start theorizing about how Batman could exist in the MHA world and what kind of Quirk he could have.
Surprise. They might be surprised to see how fans imagine different scenarios for them. For example, a character from a magical girl anime might be shocked to find a fanfiction where she's suddenly a detective in a noir - style story.
Characters' personalities play a huge role. For example, Dabi, who has a bit of a dark and brooding personality, might be drawn to the more complex and morally grey characters in Naruto fanfiction. He might relate to some of the characters who have had a tough past. In contrast, Ochaco, being a positive and empathetic character, would focus on the emotional parts of the fanfiction, like the friendships and the characters' dreams. And then there's Tokoyami, with his rather mysterious and deep - thinking nature. He'd be delving into the philosophical aspects of Naruto, such as the concept of the ninja way.
Sakura would probably be shocked. She knew the Akatsuki was powerful, and Naruto killing them all might make her see Naruto in a whole new light, perhaps as a more dangerous or powerful figure than she initially thought. Kakashi, on the other hand, might be worried about the implications. He would be proud of Naruto's strength but also concerned about the power vacuum and how it could affect the balance of the ninja world.
Harry would be completely shocked. He's known Hermione as his best friend and to see her with Lucius, who was once a Death Eater, would be almost unthinkable. He'd probably try to convince Hermione that she's made a huge mistake.