In such a fanfiction, there might be a big threat that requires both teams to combine their skills. The Flash could race with Kid Flash and share some speed - related tips. And Wonder Woman could train the female members of Young Justice in combat.
They might be really surprised. Some fanfictions could show their characters in very different ways than they expect. For example, they might see relationships between characters that they never thought of in the official story. It could be both amusing and a bit strange for them.
Batman is often a very popular character. In fanfiction, he can be portrayed in different ways, like a more nurturing mentor figure to the Young Justice team or as a master strategist leading the Justice League in complex battles.
Some of them might be amused. They could find the different takes on their characters and stories quite entertaining. For example, Superman might chuckle at a fanfic that has him in a comical situation.
A third interesting storyline might involve a secret alliance between a member of the Justice League and a villain that the Young Justice team discovers. This discovery then sets off a chain of events where the Young Justice team has to decide whether to trust the rest of the Justice League and how to handle this new information without causing a complete breakdown in the superhero community.
Superboy is often a popular choice. His complex origin story, being a clone of Superman, gives a lot of room for exploration in fanfiction. Writers can delve into his identity issues and how he fits in with both the Young Justice team and in relation to the Justice League.
Maybe a story where some of the younger members of the Young Justice team are frustrated with the Justice League's methods and decide to take on a mission on their own, but end up getting in over their heads and have to call in the League for help. This could lead to a lot of character development and some interesting dynamics between the two groups.
A cool plot could be a time - travel related crossover. The Young Justice team travels back in time and meets the younger versions of the Justice League members. They have to work together to stop a time - traveling villain from changing history in a way that would destroy the future. Or perhaps there's a magic - based crossover where a powerful sorcerer is causing chaos. The Justice League, which is more used to physical threats, has to team up with the Young Justice, some of whom have magic - related powers, to defeat the sorcerer.
The experienced members of the Justice League would likely take on a mentoring role. For example, Superman might offer advice to Superboy on how to better control his powers. Batman would probably be more cautious about involving the Young Justice team in dangerous missions, while the younger heroes would be eager to prove themselves. Aqualad could learn new underwater combat techniques from Aquaman. This would create a dynamic of growth and learning between the two groups.
It's hard to say who would win. The Justice League has more experience and raw power. But Young Justice is more unpredictable and often thinks outside the box. If it was a straight - up fight, the Justice League might have the edge in terms of power levels. However, Young Justice could use their youth and creativity to find weaknesses in the Justice League's more traditional fighting styles.