Superboy might interact with Kakashi as well. Given Superboy's strength and Kakashi's experience, there could be a lot of potential for stories where Kakashi helps Superboy understand his powers better or where they have to work together to face a powerful enemy.
Robin is often one of the main characters to interact with Kakashi. Since Robin is a brilliant strategist, he and Kakashi can have some really interesting exchanges about tactics and planning.
Miss Martian is another character that can be a main focus. In some fanfictions, she uses her powers to try and understand the inner workings of Cadmus, especially when it comes to the mental and emotional states of the genetically engineered beings there. Her telepathic abilities make her a key figure in uncovering Cadmus' secrets.
The main characters might interact with historical superheroes or villains that no longer exist in their present time. For instance, they could meet an ancient sorcerer - villain who was sealed away long ago. Dealing with such a character would test their skills and force them to think outside the box in terms of combat and strategy.
It varies a lot. Sometimes it's the core team members like Dick Grayson or Wally West. Other times, it could be less prominent characters getting more focus in the fanfic.
The interactions would be diverse. Batman from Young Justice's world might have a serious conversation with Captain America about leadership. They both lead their respective teams. Artemis could befriend Black Widow and learn some new combat skills from her.
Naruto could be often involved. Since he's Kakashi's student, he might be part of the events that keep repeating in the time loop. Kakashi could be trying to protect Naruto in different ways each time the loop occurs.
In this type of fanfiction, Wonder Girl and Robin are the key players. Wonder Girl, also known as Cassie Sandsmark, has a connection to the Greek gods which gives her powers. Robin, being the protege of Batman, has a strong sense of justice and a determination to prove himself. Their relationship can range from being friends and teammates to something more romantic in many fanfictions. They are constantly evolving and facing new challenges in the world of Young Justice, which makes them exciting characters to write about.
Some characters like Superboy might be a bit jealous of Naruto's natural charisma and the way he can easily make friends. But as they face challenges together, they would start to respect each other. Naruto would be fascinated by Superboy's strength. The more magical characters in Young Justice might be interested in how chakra is related to magic in Naruto's world. And Naruto would be eager to learn about their magic. There could be a lot of cultural exchange between the two groups, which would lead to some really interesting character interactions.
The more experienced Avengers like Captain America would likely take on a mentoring role with the younger members of Young Justice. For example, he could give advice to Robin on leadership. Meanwhile, the more powerful Avengers like Thor might be a bit intimidating to the Young Justice team at first. But characters like Superboy could be eager to prove himself against Thor in a friendly sparring match.
Supergirl's no - nonsense attitude towards fighting villains would be an interesting contrast to the more youthful and sometimes impulsive nature of the Young Justice team. Aqualad, as the leader, would have to figure out how to incorporate Supergirl into their mission plans. She might be used to taking charge in her own battles, but she would have to learn to work within the team structure of Young Justice. And the team would have to adjust to her presence. For example, her super - strength could accidentally cause damage during training sessions if she's not careful. But over time, they would all grow to respect and rely on each other.
Ben would likely be the wild card. He'd be excited to show off his alien forms to the Young Justice characters. Aqualad might be a bit skeptical at first, but Robin could be intrigued by Ben's tech. Superboy might see Ben as a rival in terms of power.