Maybe an alien that can absorb and use chakra. This would be a huge threat to Naruto and his friends. But at the same time, it could also be an interesting character because it might have a different understanding of chakra than the ninjas in Naruto's world. Naruto could try to find a way to cut off its connection to chakra or even teach it a different way to use chakra that is more in line with the ninja way.
Definitely Naruto and Twilight Sparkle. Twilight is all about knowledge and magic, and Naruto has his own unique ninja powers. They could have really deep conversations about how their powers work and share knowledge. Maybe Twilight could try to study Naruto's chakra system using her magic, and Naruto could be amazed at how Twilight's magic can do things like levitate objects and create spells.
It would probably be the Shinigami. Since it's a mysterious and powerful being from another realm, its motives and actions would be really interesting to follow.
Naruto and Izuku Midoriya would be a really interesting pair. Naruto's never - give - up attitude and Izuku's growth from a quirkless boy to a powerful hero could create some great interactions. They could learn from each other's experiences and fight side by side against villains.
Well, Naruto and Symmetra could have a really cool interaction. Symmetra is all about order and structure, and Naruto, while he has his own sense of justice, comes from a world that is very different in terms of architecture and technology. They could clash initially over their different views, but then find common ground. And of course, Naruto and Soldier: 76 would be great. Soldier: 76 is a veteran with a strict code, and Naruto's energetic and often unorthodox ways could either annoy or inspire him. They could work together to lead the team in a fight against a powerful enemy.
In a 'Naruto meets aliens' fanfic, Naruto might use his ninja skills to fight off the aliens. He could use his Shadow Clone Jutsu to confuse them and then strike with his Rasengan.
I think Anzu and Sakura would make an interesting pair. They are both strong - willed female characters. Anzu could introduce Sakura to the world of Duel Monsters, and Sakura could teach Anzu some basic ninja self - defense techniques. They could bond over their shared experiences of being friends with the main male characters in their respective series and also support each other in their own personal growth.
Definitely Naruto and the Little Sisters. Naruto has a soft spot for those in need, and the Little Sisters are in a very vulnerable position. He would probably be very protective of them, and the contrast between his energetic and positive personality and their rather timid and strange existence would be fascinating.
The interaction between Naruto and Rukia could be great. Naruto's exuberance and positive attitude could contrast with Rukia's more serious and stoic nature. They could bond over their loyalty to their friends. Maybe Naruto could make Rukia laugh with his silly antics, and Rukia could teach Naruto some of the more refined aspects of combat from the Soul Society.
It could be Naruto himself. He's so full of energy and has this unique ninja power. His presence in the Winx Club's world would be really exciting. He could bring a whole new style of fighting and a different sense of humor.
The most interesting pair might be Naruto and Superman. Superman is an all - powerful being with a strong sense of justice. Naruto also has a strong sense of justice but in a more down - to - earth, ninja - like way. They could have some great discussions about power and responsibility. Also, they could team up in battles, with Superman using his super strength and flight while Naruto uses his ninjutsu. It would be a powerful combination and a great dynamic to explore in the fanfiction.