One possible plot could be that Spider - Man is accidentally transported to the DC universe where he meets the Justice League. They initially view him with suspicion but soon realize his skills and good heart. Together, they face a common enemy like a powerful interdimensional villain who is trying to merge the Marvel and DC universes in a chaotic way.
Definitely Spider - Man and Batman. Spider - Man is this young, quippy hero with great power and responsibility, while Batman is the dark, brooding detective. Their interactions would be full of contrasts. Batman would be intrigued by Spider - Man's abilities and might try to analyze him, while Spider - Man would be in awe of Batman's gadgets and detective skills.
Maybe the plot could involve a device created by Lex Luthor that accidentally merges the two universes. Spider - Man then teams up with the Justice League to find a way to separate the universes again. During this time, he has to deal with the different personalities and powers of the League members. He might form a special bond with Batman, as they both rely on their wits and gadgets.
One possible plot idea could be a team - up between the Young Justice characters and Spider - Man. They could face a common enemy that is too powerful for either group alone. For example, a super - villain who has the ability to manipulate time and space, causing chaos in both their universes.
Spider - Man could fit in as the tech - savvy member. His knowledge of creating his own web - shooters and other gadgets could be useful for the Justice League. He could upgrade their equipment or come up with new ways to fight villains.
It could be really exciting. Imagine Spider - Man swinging into the Justice League's world. He might team up with Superman to take on a powerful new villain. Maybe they would have some initial misunderstandings due to their different ways of operating, but then quickly realize they can complement each other's skills.
Well, in such a fanfiction, Spider Man could show off his acrobatic skills to the Justice League members. Maybe he'd teach Flash a thing or two about speed and agility in a friendly competition. And he could collaborate with Batman on some detective work, combining his street - smart knowledge with Batman's high - tech resources.
The plot could start with Spider - Man being mysteriously transported to the Justice League's universe. He initially clashes with some members due to misunderstandings. But as they face common threats, they start to work together. And the harem part could develop as Spider - Man shows his heroic side. For instance, he saves a female Justice League member from a dangerous situation, and she starts to have feelings for him. Then, more and more members get involved as they get to know Spider - Man better.
Perhaps in the fanfiction, a cosmic event causes a rift between the Marvel and DC universes. Captain America and the Justice League find themselves on the same side as they are the only ones who can prevent the destruction of both universes. They must overcome their differences in ideology and power - sets. Captain America's sense of justice and the Justice League's diverse powers and abilities would make for an interesting dynamic as they work together to close the rift and defeat the forces trying to destroy the universes.
One possible plot could be that Naruto is somehow transported to the DC Universe. He teams up with the Justice League to stop an evil force that is using a combination of Naruto - style ninjutsu and advanced technology from the DC world. For example, Lex Luthor could be the mastermind behind this, having found a way to harness chakra and is using it to create powerful and dangerous weapons. Naruto's skills in combat and his ability to sense and manipulate chakra would be a great asset to the Justice League, and in return, the League could teach Naruto about their powers and technology.
One possible plot could be that Percy Jackson's world is suddenly invaded by a powerful threat that the demigods alone can't handle. So, Percy and his friends seek the help of the Justice League. The League initially doubts the existence of Greek gods and demigods but soon realizes the seriousness of the situation. They team up, with Percy teaching the heroes about the magic and monsters of his world while they teach him about modern combat and technology. Together, they fight the new threat that combines both magic and advanced weaponry.