The Arrow would be a great character to have a major role. His combat skills and leadership would be important in the fight against the threats from Earth X. And then there's Eobard Thawne. He has knowledge of different timelines and could use that to manipulate the events of the Crisis. Another character could be Martian Manhunter. His shape - shifting and telepathic abilities could give the heroes an edge in the battle.
Supergirl could have a major role. Her strength and powers would be very useful in the Crisis. She could be the one to lead the charge against the villains from Earth X. Also, Reverse Flash. He is always causing trouble and in a crossover, he could form an alliance with the villains of Earth X for his own gain.
Definitely Cisco Ramon. His ability to create new tech and his knowledge of the multiverse could be crucial. He could figure out ways to counter the threats from Earth X. Also, Kara Zor - El (Supergirl) again. She has the power to take on powerful foes. And don't forget about Earth X versions of the characters. For example, an evil version of Superman from Earth X could be a major antagonist, and the heroes would have to figure out how to defeat him.
A possible plot is centered around the relationships that form during the crossover. Imagine a love story between two characters from different Earths. Maybe a hero from Earth X falls in love with a hero from the main Earth. This relationship could be complicated by the differences in their worlds and the events of the Crisis. Also, a plot about the heroes having to adapt to the different rules and cultures of Earth X would be engaging.
In 'The Flash Crisis on Earth X' fanfiction, one of the key characters is Eobard Thawne, Reverse - Flash. His complex relationship with Barry and his knowledge of time - travel can create really interesting plot twists. Also, Sara Lance, White Canary, is important. Her combat skills and her experience with the Legends of Tomorrow team bring a different dynamic to the story. And Cisco Ramon, with his ability to create and manipulate technology, is often vital in fanfictions as he can come up with solutions to various problems.
Barry Allen is quite popular. His speedster abilities can create a lot of interesting scenarios in the Crisis on Earth X setting. Writers can explore how his powers work differently on Earth X or how he teams up with alternate versions of himself.
One aspect to consider in 'Crisis on Earth X' fanfiction could be the exploration of alternate versions of characters. Writers often take advantage of the multiverse concept in this storyline to create unique character arcs that deviate from the original canon.
An Asari scientist could be a main character. She might be intrigued by the mystery of the abandoned Earth. Her knowledge of biotics and different cultures in the Mass Effect universe could help her in deciphering the secrets of Earth. She could be the one to make the first contact with any remaining humans or discover important artifacts. Also, a Krogan mercenary could be a main character. His brute strength and combat skills would be useful in exploring the dangerous and desolate Earth. He might be in it for the loot or just the thrill of adventure.
Obviously, Baby Danvers is likely to be one of the main characters. There may also be other characters from the Earth - X universe that play important roles, perhaps some of the well - known superheroes or villains from that particular setting, but without actually reading the fanfic, it's hard to say for sure.
Fanfiction often gives the opportunity to develop secondary characters more. In the context of Crisis on Earth X, these characters can play crucial roles. They might have unique skills or knowledge that help in dealing with the crisis, and their growth and contribution can be a central part of the fanfiction story.
Definitely Hinata. She already has strong feelings for Naruto in the original Naruto series. Sakura could also be part of it as she has a long - standing relationship with Naruto. From other series, if we're doing a crossover, Erza from Fairy Tail could be an interesting addition. She's strong, independent, and would make for an interesting dynamic in a harem situation with Naruto. Also, Rukia from Bleach could be another. She has a cool and collected personality which would contrast with Naruto's more exuberant nature.
I think Rogue would be an interesting main character in a crossover. Her power - absorbing abilities could create some really unique situations, especially when she comes into contact with Clark or other powered individuals in Smallville. On the Smallville side, Lex Luthor could be a main character too. His devious nature and thirst for power could put him at odds with both the X - Men and Clark, making for a complex and engaging story.
Well, in some fanfictions, there might be a plot twist where the portals between the different Earths malfunction in a new way. Instead of just allowing the heroes and villains to cross over, they start merging certain parts of the different Earths. So you might have a city on Earth - 1 that suddenly has a section that looks like it's from Earth - X. This would create all sorts of chaos and new challenges for the characters to deal with. It also gives an opportunity for different versions of the characters to interact in unexpected ways, like a more peaceful version of a villain from one Earth having to face off against their more malevolent counterpart from another Earth that has now invaded their space.