One possible plot could be Serena discovers she's pregnant during her Pokemon journey. This could bring about a lot of changes in her goals and how she interacts with her Pokemon. Maybe she has to take a break from her usual adventures to take care of herself and the upcoming baby, and her Pokemon become more protective of her.
Perhaps in a 'Serena Pokemon Pregnant' fanfic, the pregnancy could be a result of some sort of magical or unique Pokemon - related event. The plot could then revolve around Serena trying to understand how this happened and what it means for her future. Her friends and Pokemon would be involved in helping her through this strange situation, and she might have to face some challenges related to the stigma or mystery surrounding her condition in the Pokemon world.
The plot could involve Serena encountering a Hypno in the wild. Maybe she's initially scared, but then realizes Hypno has some unique abilities that can help her in her Pokemon journey. For example, Hypno could use its psychic powers to lead Serena to rare Pokemon or hidden items.
Well, perhaps in the fanfiction, they discover Serena's pregnancy during an important Pokemon battle tournament. This news spreads among their friends and fellow trainers. Some are overjoyed and offer support, while others are a bit skeptical about how they'll manage both family and their Pokemon - related duties. They then have to figure out how to balance their passion for Pokemon with the new responsibilities of parenthood.
Well, it could start with Ash finally realizing his true feelings for Serena. Maybe they meet up again after a long time apart. Then they start to plan a small, intimate wedding in a beautiful Pokemon - filled location like a meadow full of Pikachu and Eevee. Their Pokemon friends could help with the preparations, like Pidgey delivering invitations.
One possible plot idea could be Serena starting a new Pokemon journey in Alola. She might encounter unique Alola Pokemon and have to adapt to the new region's battle styles. For example, she could participate in the Alola trials and learn about the local culture and traditions related to Pokemon.
One possible plot could be that Serena discovers she's pregnant and is initially scared. Nate, on the other hand, steps up and they decide to face this new chapter together. They start preparing for the baby, from choosing a nursery to attending parenting classes. Along the way, they face some judgment from their friends and family, but their love for each other and the unborn child helps them overcome all the obstacles.
Well, it could be that Serena gets a new flying - type Pokemon as her ride. Maybe it's a shiny Pidgeot that she discovers in a hidden forest. This new ride would allow her to travel faster across the Pokemon world and reach new regions more quickly for her Pokemon journey.
Perhaps the story could revolve around Serena getting lost in the alleys of Lumiose. As she tries to find her way out, she stumbles upon a group of Pokemon trainers having a unique battle style she has never seen before. This inspires her to develop her own new training techniques for her Pokemon.
A Litten might be a good choice for Serena. It has a fiery personality and could bring a new dynamic to her team. With proper training, it could become a powerful Fire - type Pokemon in battles against water - type opponents in Alola.
A plot idea could be that Serena discovers she's pregnant during a big Pokemon tournament. She has to decide whether to continue competing or focus on her pregnancy. Another idea is that she finds a rare Pokemon egg that has some sort of magical connection to her unborn child. Or perhaps a villain in the story tries to use her pregnancy to their advantage, thinking she'll be more vulnerable.
There could be. The Pokemon fandom is quite large and diverse. Fanfic writers love to create unique storylines for their favorite characters. Ash and Serena are popular characters, so it's not surprising that someone might write a fanfic about them having a family. But these types of fanfics may not be endorsed by the official Pokemon creators.