The plot might start with an interdimensional rift that starts causing chaos in both universes. The Avengers notice strange energy signatures and track them to the Arrowverse. Once there, they find that the Arrow and his team are already on the case but are in over their heads. The Avengers join in, and together they have to deal with not only the threat of the rift but also some villains in the Arrowverse who see this as an opportunity to take over. There could be sub - plots like Black Widow and Felicity Smoak teaming up to hack into some advanced technology that's related to the rift, and Thor and Oliver Queen having a showdown with a powerful meta - human.
One possible plot could be that the Avengers are somehow transported to the Arrow's universe. Maybe a villain in the Arrowverse has acquired a powerful artifact that creates portals, accidentally pulling in the Avengers. Then, they team up with Arrow and his team to fight against a common enemy, like a new super - powered threat that neither group could handle alone.
In a fanfic crossover, perhaps there's a threat in the Avengers' world that requires some special skills only the Arrow and his team possess. So, Iron Man figures out a way to cross dimensions and recruits them. The story could then revolve around the clash of different fighting styles and personalities. For example, Hawkeye and Green Arrow comparing their archery skills, while Captain America tries to instill his sense of justice and leadership in the Arrow's team. It could be a really interesting exploration of two very different superhero universes coming together.
One possible plot could be that Oliver Queen gets transported to the Avengers' universe. He teams up with Hawkeye, sharing their archery skills and combat tactics. They could go on a mission to stop a new threat that combines the technology of the Arrowverse and the super - powered enemies of the Avengers.
A possible plot could be that Oliver Queen from Arrow gets transported to the Marvel universe where the Avengers operate. He might initially be seen as a threat, but then he teams up with the Avengers to fight a common enemy. Maybe a villain that has powers related to both the technology in Arrow and the superpowers in the Avengers' world.
Another idea is that a villain creates a rift between the two universes. The Avengers and Merlin have to team up to close this rift. During their journey, they exchange skills and knowledge. Black Widow could teach Merlin some combat skills, while Merlin could show the Avengers how to use magic in a more strategic way. This way, they not only close the rift but also become stronger as a combined force.
One possible plot could be that Batman's Gotham is threatened by a powerful villain who has some connection to the Avengers' universe. Maybe Loki decides to cause chaos in Gotham as part of a larger plan against Earth. Batman, being the detective he is, starts to investigate and soon realizes that this is no ordinary criminal. He then somehow gets in touch with the Avengers, perhaps through SHIELD's intelligence network. Together, they combine their skills and resources to take on Loki and his minions. Batman's stealth and strategic mind would complement the Avengers' superpowers.
The plot might involve a villain who has the ability to manipulate time or space. This causes disruptions in both the Marvel Universe and Green Arrow's world. The Avengers, with their superhuman powers and high - tech gadgets, and Green Arrow, with his street - smart skills and archery expertise, must find a way to stop this villain. They might have to travel between their respective universes, which could lead to some really interesting cultural clashes and misunderstandings.
Well, one possible plot could be that the gods in the Percy Jackson universe notice some strange energy disruptions caused by the Infinity Stones in the Avengers' world. Percy and his friends are sent to investigate. They meet the Avengers and at first there are misunderstandings, like the Avengers thinking Percy's powers are from some new form of alien technology. But then they realize they need to work together to stop a common enemy, perhaps a new powerful being that is drawn to the combined power of the demigods and the Infinity Stones.
One possible plot could be that a powerful villain from another dimension threatens both the DC and Marvel universes. Superman and the Avengers have to put aside their differences and combine their powers. For example, Superman's super strength and flight could be paired with Thor's godly abilities and Captain America's leadership. They could start off not trusting each other, but as the battle progresses, they learn to work together and defeat the villain in an epic showdown.
One possible plot could be that the Avengers are somehow transported to the Naruto universe. They team up with Naruto and his friends to fight a common enemy like Kaguya who has somehow obtained the Infinity Stones. The Avengers' powers and technology would be a huge shock to the Naruto world, and they'd have to learn to combine their skills to succeed.
A cool plot could be that a villain creates a device that can manipulate time. This device causes chaos as it starts to merge different timelines. Spider - Man gets caught in the middle of this temporal mess while on a normal patrol in New York. He then reaches out to the Avengers for help. The Avengers, who have experience with time - related issues from previous adventures, team up with Spider - Man. Thor uses his lightning to disrupt the device's power source, while Spider - Man swings in to physically disable it with the help of Black Widow's combat skills. In the end, they manage to restore the timelines and save the day.
Maybe it could be a time - traveling criminal. This villain has the ability to jump between different timelines and has noticed that by disrupting the key events in both the Arrow and Avengers universes, he can create chaos and then rule over the resulting mess. He would constantly be one step ahead of the heroes as he could manipulate time to his advantage. He could also use his knowledge of future events to set traps for the Avengers and the Arrow team.