Naruto and Aang would be the most obvious ones. They are the main characters in their respective worlds.
Iruka sensei from Naruto might interact with the Avatar's teacher, like Gyatso. They are both mentors and could share their experiences in teaching their students. And Kakashi could have some interesting encounters with some of the more experienced benders in the Avatar world, perhaps learning from them about different ways to control energy.
Sasuke from Naruto could also interact with characters like Zuko from Avatar. They both have a dark past and a journey of redemption. They might start off as rivals but then find common ground in their desire to protect what they care about. Also, Sakura could meet Katara. They are both strong female characters and could exchange knowledge about healing and combat techniques.
Probably Naruto and Tracer. Naruto is always eager to meet new people and make friends, and Tracer's curious and friendly nature would make her approach Naruto. They could start by comparing their abilities. Naruto would show off his Rasengan while Tracer might do a quick display of her blinking ability.
I think Mirabel from Encanto and Aang from Avatar would be likely to interact. Mirabel is all about finding her place in the family and Aang is on a journey to save the world. They could share their experiences of feeling different and having big responsibilities.
Kakashi could also be a character involved in interactions. His calm and observant nature would make him a good mediator between the two groups. He might be interested in learning about the monster musume's abilities and how they could potentially be used in the ninja world. Rock Lee might also be a candidate. His enthusiasm and determination could be an interesting contrast to the monster musume, and he could potentially learn new fighting styles from them or teach them his own.
Probably Naruto and Robin. Robin is the leader - type in Young Justice, always thinking and strategizing. When Naruto shows up, Robin would be the one to approach him first, trying to figure out who he is and what his intentions are. Naruto, being friendly and curious, would be open to the interaction.
Iron Man is another candidate. Tony Stark's technology and Naruto's ninja techniques could be a great contrast. They could learn from each other. Stark might be interested in Naruto's chakra - based powers and try to replicate them in some way, while Naruto could be amazed by Stark's high - tech gadgets.
Definitely Naruto and the Punisher first. Naruto would be intrigued by the Punisher's methods and would try to understand his motives. It's also possible that Sakura could interact with the Punisher. She's a strong - willed character, and she might try to either stop the Punisher if she thinks his actions are too extreme or help him if she sees the good in his goals. And Jiraiya might also be a character who could cross paths with the Punisher. Jiraiya's worldliness and his own sense of right and wrong could lead to some deep discussions between them.
Well, obviously Naruto himself would be the main character. There could also be his friends like Sasuke and Sakura, who might be involved in the interactions between the two Narutos. Maybe they are confused at first by seeing two Narutos, but then they help them figure out what's going on.
Probably Naruto and Twilight Sparkle. Twilight is the intelligent and curious one in the My Little Pony world, always eager to learn new things. Naruto, with his unique ninja abilities, would be something completely new for her. She would likely approach Naruto first to find out more about him.
Probably Ash and Iron Man. Iron Man is always curious about new things and Ash with his Pokémon would be quite an interesting sight for him. He'd likely approach Ash first to ask questions about what he is and what those strange creatures are.
Spyro and Twilight Sparkle would be likely to interact. Twilight is very intelligent and well - versed in magic, and Spyro has his own dragon powers. They could learn from each other. For example, Twilight could study Spyro's dragon magic, and Spyro could learn about the complex magic system in Equestria from Twilight.