His Pokémon are central, as they are always by his side. Pikachu would be a key figure in any story related to Ash. Then there are his human friends. Brock could be involved in cooking for Ash, which might contribute to the weight gain. Misty could be there to comment on Ash's appearance and give her opinions. And in some fanfictions, Nurse Joy or Professor Oak might also be included to provide medical or wise advice regarding Ash's situation.
Misty and Brock are also main characters in many of these fanfictions. After Ash's sacrifice, they might be the ones to comfort Pikachu and the other Pokémon. They could also take on Ash's unfinished tasks, like continuing to explore the Pokémon world, helping other trainers, and fighting against any emerging threats. Their friendship with Ash gives them the motivation to keep going in his absence.
In this fanfiction, Gary could be an important character. Since he has always been in competition with Ash, he might have mixed feelings about Ash being the chosen one. Serena could also be a main character. She might be inspired by Ash's chosen - one journey and decide to follow him, offering her own skills and support. Professor Oak would likely be involved as well, guiding Ash with his vast knowledge of Pokémon.
Well, often the fanfiction might explore how Ash's eating habits change to lead to the weight gain. It could also show how his self - confidence is either affected negatively or he overcomes the insecurities related to his new body. And sometimes, there could be a theme about his friends' reactions to his weight gain, whether they are supportive or not.
Quinn Fabray could be involved too. Given her history of being concerned about her looks and status, a weight gain story for her could be about her learning to love herself regardless of the number on the scale. It could also involve her relationship with the other Glee club members as they support her through the process.
Well, obviously Tails is the main character as it's about his weight gain. But Sonic often shows up in these fanfictions too. Sonic might be there to support Tails, or he could be initially confused about what's happening to his friend. Another character could be Dr. Eggman. He might be the cause of Tails' weight gain, either intentionally through some evil plan or accidentally because one of his inventions backfires.
In some 'pokemon champion ash fanfiction', Gary could be an important character. He has always had a competitive relationship with Ash, so in stories where Ash is a champion, Gary might try to challenge him or be involved in some sort of plot related to Ash's championship. Another character could be Serena, especially if the fanfiction focuses on the romantic aspect of Ash's life along with his championship journey.
In many fanfictions, Gary Oak can also be a significant character. Since Ash is smart in these stories, there could be a rivalry between him and Gary where they constantly outwit each other in Pokemon battles and in their knowledge of Pokemon lore. Another character could be Professor Oak, who might be amazed at Ash's new intelligence and give him special tasks or Pokemon to train.
The main characters also include Ash's mother in some fanfictions. She might be worried about Ash's newfound powers and his connection to Goku. In the Dragon Ball universe, Kami could be involved. He could sense Ash's unique existence as a Pokémon - Saiyan hybrid and either try to help him or be wary of his potential. And of course, there are always the various villains from both universes that could be a threat to Ash in these fanfictions.
Twilight Sparkle is often involved. As a central character in the My Little Pony universe, her studious and sometimes self - conscious nature can be interesting to explore in the context of weight gain. Pinkie Pie could also be a main character as her love for parties and food might lead to some scenarios of weight gain. And Rainbow Dash, with her athletic build, could have an interesting character arc if she were to experience weight gain, perhaps struggling with her identity as an athlete.
Brock could also be a main character. Since he has knowledge about Pokémon care and breeding, he could be Ash's colleague in the fanfiction. They could work together on projects related to Pokémon health and nutrition.