What could be a great plot for a Prototype crossover Justice League fanfic?

Another possibility is a more comical crossover. The Flash tries to race a Warthog from Halo and fails miserably because he doesn't understand the vehicle's controls. Or Batman trying to figure out the technology of Halo's weapons and getting all confused. This kind of fanfic would be full of humorous moments and cultural clashes between the two universes.

One idea could be that Voldemort discovers a way to enter the DC universe and teams up with some of the Justice League's villains like Lex Luthor. The Hogwarts students and the remaining members of the Justice League have to join forces to stop them. The wizards can use their magic while the superheroes use their powers.

The plot could start with Vegeta being exiled from his own planet due to some political intrigue. He ends up on Earth, where he crosses paths with the Justice League. At first, there is tension as the League is unsure of his intentions. But when a powerful enemy, like Darkseid, starts to target Earth, Vegeta decides to help. He teams up with Superman, and they have an epic battle of strength. Meanwhile, Batman uses his detective skills to figure out a weakness in the enemy's plan. Wonder Woman, Aquaman, and Flash also play their parts, with Vegeta adding his Saiyan speed and power to the mix. In the end, they defeat the enemy, and Vegeta decides to stay on Earth for a while to learn more about these strange heroes.

One possible plot could be that the Hulk is somehow transported to the DC universe and is initially seen as a threat by the Justice League. They might try to subdue him, but then realize he's not entirely a villain. Maybe there's a common enemy that forces them to team up. For example, a powerful alien force that is causing destruction in both the Marvel and DC universes. The Hulk's brute strength combined with the Justice League's diverse powers could make for an epic battle against this enemy.

One possible plot could be that the Omnitrix malfunctions and sends Ben 10 to the Justice League's universe. The Justice League initially views Ben as a threat due to his alien forms. But as they learn more about him and the threat of an inter - dimensional villain, they team up. Ben's different alien forms offer unique skills that complement the League's powers, and together they fight the villain to save both universes.

Definitely Alex Mercer. His powers are so unique compared to the Justice League members. He can shapeshift into anyone, has superhuman strength, and can regenerate from almost any injury. This would create a lot of interesting interactions with the League. For example, he could transform into Superman to test the limits of his own power against the real Superman, which would lead to a really cool showdown.

Well, it could be about the Pokemon joining forces with the Justice League to fight a common enemy. Maybe a powerful villain is threatening both the Pokemon world and the cities protected by the Justice League. The Pokemon could use their unique abilities like Pikachu's electricity or Charizard's fire-breathing in combination with the superpowers of the Justice League members such as Superman's strength or Batman's gadgets.

The plot might involve Spiderman's scientific knowledge impressing Batman. He could work with Cyborg to create some new tech to combat a threat. And his quick - witted banter would add a new dynamic to the usually serious Justice League. For example, he might crack jokes during a battle, which at first annoys the others but later they come to appreciate it as a way to ease the tension.

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 that the Justice League discovers a strange energy signature that turns out to be Iron Man's arc reactor. They track it down and find Iron Man. Iron Man is initially out of his depth in this new world of superpowers. But he uses his wits and technology. For example, he could upgrade the Flash's suit to make him even faster, and in return, the Flash helps him understand the new world he's in. Together, they all face off against Darkseid who has plans to invade both universes.