Let's say you become a deer. Your character could develop the ability to sense danger from afar. This could be because deer in the Naruto world have a natural instinct for self - preservation. You could also develop the ability to blend into the forest better, like using your antlers to create a kind of camouflage. Another way to develop abilities is by making pacts with other creatures or spirits. If you make a pact with a water spirit, you might gain the ability to control water in some way, even if you're just a simple forest deer.
If you become an animal in this fanfiction, your character could develop new abilities through training. For example, if you're a wolf, you could train to run faster and have better endurance in the wild. You might also learn how to communicate with other animals in the forest, which could be a useful ability for gathering information.
If you become a dog in this Naruto fanfiction, your sense of smell can be a huge asset. You could use it to track down missing ninjas. For instance, when Sasuke leaves the village, your dog -character could pick up his scent and follow it. This would create a new sub -plot where you try to convince Sasuke to come back. Your animal ability to smell emotions in a way could also be used. You might be able to sense Sasuke's inner turmoil and use that knowledge to try and reach him on an emotional level.
Naruto himself would be the most interesting. Just imagine him, with his energetic and determined personality, now having this strange connection to the song. His singing would be so out of character for him, yet at the same time, it could add a whole new dimension to his character, showing a more artistic and emotional side that we haven't seen much of before.
Naruto's understanding of the ninja world would deepen. With the new doujutsu, he could see things that were hidden from him before. This would make him more aware of the politics and power struggles in the ninja villages. He might start to question some of the long - held beliefs and traditions. He could also use his new insights to try and bring about positive change in the ninja world, like finding ways to end the cycle of hatred between different clans.
Naruto would become more strategic. With the Ope Ope no Mi abilities, he can't just rely on his brute strength and chakra. He has to think about how to use the powers effectively. For example, when using the room creation, he needs to consider the size and location to maximize its impact on his enemies.
If Naruto and Fuu had children in a fanfiction, their kids' abilities would develop in an interesting way. Naruto's natural talent for making friends and his strong chakra would influence them. They could easily make allies and have a large reserve of chakra. Fuu's stealth and her ability to adapt quickly would also be passed on. So, the children might be able to quickly learn new jutsu and use them effectively in combat situations. They'd grow up learning from two very different but powerful ninja, which would make their abilities diverse and formidable.
Well, Naruto would be extremely overpowered. He could probably fly around the Hidden Leaf Village instead of using his normal ninja transportation methods. His strength would be off the charts, allowing him to easily lift huge boulders or even buildings without using chakra. His speed would also be enhanced, making him almost uncatchable in combat. This new set of abilities might make him a bit more reckless at first, as he gets used to the power, but over time, he would learn to use it more responsibly.
If Karin had Kryptonian abilities, her confidence would likely soar. She could become more assertive in her actions. For instance, with super strength, she would no longer be as afraid in combat situations. Her character might also become more isolated at first as she tries to figure out her new powers on her own, not wanting to endanger her friends. But as she masters them, she would be more open to sharing and using them for the good of the group.
Through intense battles on the battleship. In the heat of combat, Naruto might discover that he can use his Nine - Tails chakra in a new way to boost the power of the battleship's engines or shields, which is a new ability born out of necessity.
Sakura would likely become more confident. Having Tobirama's abilities would give her an edge in battles and in the ninja world in general. This newfound power would make her feel more capable and less reliant on others, which would boost her self - esteem.
His physical abilities would likely improve a great deal. Black Widow is a master of martial arts, so Naruto could become even more formidable in close - quarter combat. His agility and strength could be enhanced beyond what he achieved in the ninja world just through her training methods.