Kara Zor - El, Supergirl, is a significant character in the Arrowverse graphic novel. She has all the powers of Superman and is a powerful protector of National City. Also, Cisco Ramon, with his tech - based powers, is often a key player. He helps the heroes with his inventions and his ability to open breaches between different dimensions.
Batman himself is obviously one of the most popular. Fans love to see how he would be written in the Arrowverse context. Another popular character would be Alfred. His relationship with Batman and his role as the caretaker and advisor always adds depth to the story. And also, characters like Catwoman might be popular as she brings in the element of mystery and romance to the fanfictions.
Oliver Queen (Green Arrow) and Black Widow are often paired. Oliver's combat skills with his bow and arrow combined with Black Widow's martial arts and espionage skills make for an exciting duo. They could be on a mission where they need to infiltrate an enemy base and use their complementary skills to succeed.
Superboy is often a popular character. His struggle with his identity as a clone and his relationships with other characters like Miss Martian make for great fanfiction material.
The Arrowverse takes inspiration from the comics, but it's not a one-to-one canon. Writers and producers make choices to create a unique and coherent TV narrative, which means not all comic details are followed precisely.
Definitely Oliver Queen. His skills as a vigilante and his leadership qualities would make him a great addition. He could be leading the fight against the tyranny on Earth X. Another is Supergirl. Her superpowers would be a huge asset in the battles on Earth X. And of course, Harrison Wells, his intelligence could be used to develop strategies against the Earth X enemies.
The Arrow's archery skills combined with Hawkeye's would be really interesting. They could come up with new types of arrows together. And if you think about it, characters like Iron Man could provide technological upgrades to the Arrowverse heroes' gadgets. For instance, he might improve the Flash's suit to make it more energy - efficient or give Green Arrow some high - tech arrows with advanced tracking capabilities. There are so many ways their powers and skills could interact in really cool and unexpected ways.
Another way is through shared villains. Say a villain has the ability to travel between the two universes and is causing chaos in both. This would force the heroes to come together. For instance, Loki could find a way to the Arrowverse and start causing trouble. The Arrowverse heroes would be out of their depth dealing with a god of mischief, so they call in the Avengers for help. The two groups would have to learn about each other's abilities and strategies to take on Loki.
In a crossover, Archie's relationship with his friends might change. He's used to being the football star in Riverdale, but in the Arrowverse, he could be in awe of the superheroes. His friendship with Jughead might be tested as Jughead tries to keep Archie grounded while Archie is excited about the new world. Betty and Veronica's relationship could also shift. They might compete in a different way, like trying to impress a certain Arrowverse hero. Their friendship could become more competitive or they could find new common ground in helping the heroes.
They often explore deep emotional connections between male characters. For example, they might show how two characters support each other through tough times in the Arrowverse.