In the X - Men fanfiction, Harry Potter's enhanced senses could be a new factor in mutant - human relations. His ability to sense things differently might make mutants see humans in a new light. Maybe he could sense the emotions of mutants more acutely, which could lead to better understanding between the two groups. Also, his enhanced senses could be used in training new X - Men recruits. He could detect their potential and areas of improvement more accurately than normal humans.
He might become a target. If there are villains in the X - Men universe who don't want someone with such powerful senses around, they could try to take him out. His enhanced senses could also make him a bit of an outcast among normal humans in the fanfiction world, as they might not understand his abilities.
Often, his enhanced hearing could be depicted as being able to pick up on whispered spells from a distance. It might be described as an extension of his natural magical abilities. Maybe he can sense danger approaching through a tingling in his senses, like a premonition but more acute due to his enhanced senses.
She could be a mutant with a unique power that was previously unknown. For example, maybe she has the ability to manipulate technology in a way that's useful to the X - Men. She could use her skills to hack into enemy systems or enhance the X - Men's own tech.
Sunset Shimmer's powers might be a bit different from the typical mutant powers in the X - Men world. But that's what makes it interesting for a fanfiction. She could potentially be a bridge between the magical and mutant worlds. For example, if there are threats that involve both magic and mutant - hating forces, she could use her skills to unite the X - Men with other magical beings. Her power of teleportation, which she has in her own story, could be enhanced in the X - Men fanfiction and used to quickly move the X - Men around during missions.
If the X - Men were in the Frozen universe, they would bring a new dynamic. Wolverine's healing factor would make him a valuable asset in the cold and dangerous environment. He could withstand extreme cold and any injuries that might come from the ice. Storm could collaborate with Elsa to create more elaborate weather patterns. The X - Men's mutant status could also cause some interesting reactions among the people of Arendelle, who are not used to such extraordinary abilities. It could lead to a story about acceptance and cooperation between two very different groups.
One way it could work is that there's a cross - over event. A powerful wizard or mutant creates a portal between the two universes accidentally. Harry Potter steps through it and something in the X - Men world affects his magic, giving him cat ears. Or perhaps there's a mutant in the X - Men world who has the power to transform others and they transform Harry into having cat ears as a joke, but then he has to deal with the consequences in both worlds.
Naruto would be a very unique addition to the X - Men universe. His godlike powers would make him stand out among the mutants. He could use his speed and strength, similar to some of the more powerful mutants like Wolverine or Colossus. But his ninjutsu would be completely new to the X - Men. He could teach them about stealth and deception, which are important ninja skills. Also, his strong sense of loyalty and friendship would fit well with the X - Men's values of acceptance and teamwork.
One challenge could be sensory overload. With enhanced senses, there would be so much more information coming in. For example, in a crowded Hogwarts corridor, he might be bombarded with all kinds of smells, emotions, and sounds. This could be overwhelming and make it difficult for him to focus on important things like his studies or a mission.
In an X - Men fanfiction with an immortal Naruto, his powers would blend in an interesting way. Naruto's immortality might be seen as a super - power in the X - Men world. His ability to constantly regenerate and not die could be a mystery to the mutants. His other powers, such as being able to control the Nine - Tails' chakra, would add another layer of complexity. He could use the Nine - Tails' power to match up against some of the strongest mutants. And his experience as a ninja from his own world could bring a new perspective to the X - Men's way of handling threats.
Well, Naruto's immortality would give him an edge in the X - Men universe. His ninja skills like shadow clones could be used in really creative ways during battles. For example, he could send out clones to distract enemies while the real Naruto sneaks up on them. Also, his chakra powers might be seen as a new form of energy in the X - Men world, and some mutants might be curious or even afraid of it.