Definitely Ruby and Sapphire themselves. They are the main characters and fans love to explore more about their adventures. Another popular one is Wallace, the Gym Leader. His elegance and strong Pokemon make him a great character to write about. And of course, the villains from Team Aqua and Team Magma are often featured as they add a lot of conflict to the stories.
One idea could be exploring an alternate universe where the starters of Ruby and Sapphire have different evolutions. Another could be a story focused on a side character from the manga, like giving a backstory to a Gym Trainer. Maybe also a story where the legendary Pokemon Groudon and Kyogre form an unexpected alliance instead of their usual rivalry.
Ruby and sapphire are quite different in the ORAS manga. Their appearances, abilities, and the way they interact with other characters all set them apart.
One common theme is friendship. Ruby and Sapphire often start as acquaintances or rivals and develop a deep friendship through their Pokemon - related adventures. Another theme is growth. They both grow as trainers and as individuals throughout the story.
Brendan and May are popular as they represent the players' experience in the game world. People like to expand on their adventures, give them new challenges, and develop their relationships with other characters. Among the villains, Team Magma's Maxie and Team Aqua's Archie can be really popular. Their extreme ideas about changing the world for their respective Pokemon (Groudon for Maxie and Kyogre for Archie) create a lot of room for interesting storylines in fanfiction. Additionally, Wally, the shy but determined trainer, is also a favorite in some fanfictions as he has a lot of potential for character growth.
One interesting plotline could be a trainer's journey in the Hoenn region with a unique team composition. For example, a trainer might focus on using only underrated Pokemon to prove their strength. Another could be a story about the relationship between the legendary Pokemon in Ruby and Sapphire, like how Groudon and Kyogre's rivalry affects the region. And there might also be a plotline where a character discovers a hidden power within themselves while exploring the Hoenn region's mysteries.
Definitely May and Brendan. They are the main protagonists in the games, so a lot of fanfiction writers like to use them. Another popular character is Steven Stone. His cool and mysterious nature makes him a great addition to many stories.
A really interesting plot for a Pokemon Ruby and Sapphire fanfiction could be set in an alternate Hoenn region. In this version, the roles of certain Pokemon types are reversed. For example, Water - type Pokemon are rare and Electric - type Pokemon are the dominant force in water - based areas. The main character could be a trainer who has to adapt to these new rules. They might have to find creative ways to battle and train their Pokemon. This could lead to some really unique and exciting adventures, as they encounter different challenges and make new friends and enemies along the way.
Brendan and May are often popular. They are the main characters in the original games, so in fanfiction, they are frequently the protagonists in new adventures, whether it's exploring uncharted areas or solving mysteries related to Pokemon.
One interesting plot could be a trainer's journey to discover a rare and powerful Pokemon that is said to exist only in the Ruby and Sapphire regions. They face many challenges and meet unique characters along the way.