Perhaps an older human man who has a lot of wisdom. He could be like a mentor to the younger human pets. He remembers the old world before they became pets and uses his knowledge and experience to guide the others in their fight for freedom, and also to help them preserve their humanity in this difficult situation.
Well, it could be about a world where humans are turned into pets by some powerful alien race. Maybe the story focuses on a group of humans trying to break free from this pet - like existence and fight back against their alien masters.
The plot could involve the Martians believing that humans are a new form of entertainment as pets. They start to breed humans in captivity for different 'pet' qualities. But a group of humans discovers an ancient Earth technology that can nullify the Martians' power. They then have to decide whether to use it for their own escape or to try and free all of humanity. Along the way, there would be betrayals, alliances, and lots of tense moments as the humans try to outmaneuver the Martians.
Kait Diaz could also be a main character from the human side. Her connection to the locusts through her family history could help bridge the gap between the two races. For the locusts, perhaps a young, more open - minded locust who is not as set in the ways of war against the humans. This character could be the one to convince other locusts to join the alliance. They could form a sort of friendship with Kait and together try to make the alliance work.
Judy Hopps and Nick Wilde would surely be main characters. They are the protagonists in Zootopia and their dynamic personalities would make for great interactions in the human world. They could be the ones to bridge the gap between the two worlds, with Judy's determination and Nick's street - smartness.
In this fanfiction, perhaps the Martians in 'War of the Worlds' start to keep humans as pets. It could be a dark scenario where humans are stripped of their freedom and made to serve the Martians' every whim. Maybe some humans try to rebel against this new order, leading to an interesting struggle between the captors and the captives.
Rebel leaders could be main characters in a World War 3 game story. They might be fighting against an oppressive regime that is part of one of the warring factions. These rebels could be from areas that have been marginalized or exploited. Another type of main character could be scientists. In a world at war, scientists could be working on developing new weapons, or they could be trying to find a way to end the war through some scientific breakthrough, like a new form of energy that could make the fight over resources obsolete.
Soldiers on the front lines. They are the ones directly involved in the combat, facing the danger and making split - second decisions.
Shepard could be a main character. Given their experience in uniting different species and facing great threats, they would be a natural fit in a world war scenario. They could lead a coalition against a new enemy.
Loki would be the main character for sure. And his pets, though we don't know exactly what they are yet, would also be important characters.
Often, there's a human military leader. He's the one who has to make tough decisions during the war, like whether to engage in a battle or try for peace. Then there could be a turian diplomat who is trying to understand humans better.