A cool plot could be a race between The Flash and Gotenks. They both pride themselves on their speed, so it would be interesting to see how that pans out. Also, perhaps Vegeta could befriend Batman as they both have that brooding, serious personality. They could exchange combat and strategy tips. And what if the Dragon Radar was used by the Justice League to track down an energy source that was causing chaos in both universes?
Well, in a dbz justice league fanfiction, there could be a plot where the power levels of the Justice League members are measured using the scouters from DBZ. This could lead to some interesting reactions. Superman might have an off - the - charts power level that astonishes the Z - fighters. At the same time, the Justice League could learn some ki - based techniques from the DBZ characters. For instance, Aquaman could learn how to fly using ki, which would be a huge advantage for him in underwater and above - water battles.
A crossover with the Avengers. Picture the Justice League and the Avengers having to work together to stop an interdimensional threat. There would be clashes in leadership styles between Captain America and Superman, and also a lot of cool moments as different power - sets are combined to fight the enemy.
One idea could be that the Young Justice team gets accidentally transported to an alternate dimension where the Justice League has turned evil. The Young Justice members then have to figure out how to reverse the situation while also evading capture from their once - heroes. Another could be a time - travel plot where the Young Justice team travels back in time and teams up with the early days of the Justice League to stop a threat that was thought to be long gone but has resurfaced in their own time. A third idea is that a powerful new villain emerges who can only be defeated by a combined effort of the Young Justice and Justice League, but first they have to overcome their differences in fighting styles and leadership.
One idea could be a tournament where the Z - fighters from Dbz and the Justice League members compete. For example, Goku could be paired against Superman in a friendly yet intense battle to see who is stronger in terms of physical strength and combat skills. Another plot could involve a common enemy that forces the two groups to team up. Maybe Darkseid and Frieza form an alliance and the combined forces of the Dbz characters and the Justice League have to stop them.
One idea could be that the Covenant from Halo discovers Earth while the Justice League is busy dealing with a local threat. The League has to quickly adapt to this new alien threat that has far more advanced technology than most of their foes. They might have to team up with Master Chief, who is also on a mission to stop the Covenant's invasion plans.
Well, a cool plot could be that some sort of cosmic event has merged their universes in a strange way. Members of the Avengers start showing up in the Justice League's world and vice versa. Iron Man could team up with Batman to figure out how to reverse the situation while Thor and Superman have an epic showdown that ends in mutual respect. And then they all work together to fix the messed - up universes.
One idea could be that a powerful cosmic threat emerges that neither the Justice League nor the Avengers can handle alone. So they have to combine their forces. For example, Superman and Thor could team up to take on a super - strong enemy, using their strength and lightning powers respectively. Batman and Iron Man might start off butting heads as they both think they have the best strategies, but eventually work together to outwit the villain's high - tech defenses.
One idea could be that the Young Justice team has to prove themselves to the Justice League during a major alien invasion. The League initially doubts their abilities but as the battle progresses, they see the unique skills and teamwork of the young heroes.
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.
Maybe a villain from the Justice League's rogues gallery teams up with an Avengers foe. Let's say Lex Luthor and Doctor Doom. They create a device that can swap powers between heroes from both teams. This leads to some really fun and chaotic situations. For instance, Captain America with the Flash's speed or Wonder Woman with the Hulk's strength. The two teams have to figure out how to work with their new, swapped powers and stop the villains.