You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of Pokemon fanfictions, and you can search specifically for ones where Ash gets strong.
Often, there are plotlines where Ash teams up with unexpected allies. He might join forces with a group of trainers who have different skills and knowledge. Together, they face powerful opponents and through these experiences, Ash learns new techniques and strategies, thus getting stronger. It could also involve Ash mentoring a younger trainer and in the process, he discovers new ways to improve himself.
A strong Ash usually has unique bonds with his Pokemon. These bonds are deeper than in the regular series and allow for more powerful combined attacks. He might understand his Pokemon's feelings and needs better, enabling them to perform at their peak in battles.
Maybe it's a legendary Pokemon in disguise. In some fanfictions, legendary Pokemon often play important roles. It could give Ash the egg as a test or because it senses that Ash has a pure heart. Another possibility is that it could be a young trainer who can't take care of the egg anymore and trusts Ash to do a good job.
Misty is a very likely candidate. She has been with Ash from the early days of his journey. They have a deep bond and have shared many adventures together. Their relationship has always had a bit of a romantic undertone, so in a fanfiction, it would make perfect sense for them to get married.
I'm not aware of any non - inappropriate 'Ash gets a Pokemon pregnant' fanfiction. This concept is not in line with the family - friendly nature of the Pokemon franchise. Fanfictions usually revolve around themes like battles, training, and the bonds between trainers and Pokemon. A concept like this is quite abnormal and would not be easily found in the realm of proper fan - created works.
Often, it's shown as a visible glow around Ash. This glow can be different colors, like a bright blue or a fiery red. It might pulsate when he's excited or focused during a battle.
In this fanfiction, it could be that Ash's marriage is a way to bring peace between different regions. He marries a princess or a powerful trainer from a rival region. Their union symbolizes the unity of Pokémon trainers everywhere. The story could then detail the political and social implications of their marriage, as well as the more personal aspects like their relationship building and how they learn to love and respect each other's Pokémon.
In this fanfiction, Ash might take really good care of the Pokemon egg. He would probably keep it warm and safe, waiting eagerly for it to hatch. Maybe he'd even talk to the egg, like he does with his other Pokemon friends.
A strong bond between Ash and his Pokemon is crucial. For example, Pikachu has always been by Ash's side, and their unbreakable bond gives them an edge. Their understanding of each other allows for better coordination in battles.