He might be amazed. Naruto is used to his own world and seeing a fan - made interpretation like an AMV fanfiction would be like seeing a new side of his story.
There's a fanfic where Elsa is like a quirk user in the BNHA universe. It delves into how her ice powers would be perceived in a world full of heroes and villains. It's really creative in terms of world - building and character development.
One interesting concept could be the combination of different powers. For example, Elsa's ice powers in the 'Frozen' universe interacting with the Quirks in 'BNHA'. Maybe characters from 'BNHA' could learn to control ice in new ways from Elsa, or Elsa could gain a Quirk-like ability in the crossover.
It also offers a chance for new storylines. For example, the heroes from BNHA could help the characters in Frozen deal with a new threat that their magic alone can't handle. Or vice versa, Elsa's powers could be a great asset in the BNHA world. There are so many possibilities for adventure and growth in these fanfics.
The Bnha universe's reaction would be mixed. Those who are into complex stories, like Todoroki, might study the relationships in Hamilton fanfiction. But others, like Mineta, might not be interested at all because it doesn't have much to do with his usual interests. Overall, it would depend on the individual characters' personalities and interests.
However, All Might also has to be considered. His One For All Quirk gives him superhuman strength, speed, and durability. If he were to face off against Elsa, he could potentially use his physical abilities to break through her ice. But Elsa's power is more versatile in terms of creating different ice formations and manipulating the environment.
Some would be inspired. Characters like All Might might see Peter Parker's journey as similar to his own in some ways. Both are trying to do good in a world full of challenges. All Might could appreciate Peter's determination to protect his city despite having a normal life outside of being a hero.
For heroic - centric fanfictions, they would likely be disdainful. Since they oppose heroes, seeing stories that glorify heroes would annoy them. They might scoff at the idealized versions of heroes in those fanfictions.
Some characters might be critical. Elsa, being a powerful and responsible character, might not like it if the fanfiction misrepresents her in a way that goes against her values. She might think that the writers should be more respectful of her character arc and not make her do things that are completely out of character just for the sake of a wild story. However, at the same time, she might also appreciate the creativity in some parts.
Batman would probably be very observant. He'd quickly assess the situation, looking for any signs of danger or foul play. If the ice thaw was causing problems in the Frozen world, he'd start formulating a plan to deal with it.