There could be a fanfiction where Treecko evolves in an unexpected way while with Ash. For example, it might evolve during a battle against a powerful opponent, and this new form gives Ash an edge in his Pokemon journey. In this story, Ash and Treecko's bond also deepens as they face the difficulties together.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. These platforms have a large collection of Pokemon fanfictions, and you can easily search for ones specifically about Ash and Treecko.
The relationship can develop through shared experiences. For example, if they face a tough battle together and have to rely on each other's skills to win. Ash could learn about Treecko's unique needs and habits, like what kind of food it prefers or the best environment for it to rest. This shows his care for Treecko.
Treecko in Pokemon Mystery Dungeon is really cool. A great fanfiction could be about Treecko's journey in the mystery dungeon. Maybe it could start with Treecko being a bit scared but then growing braver as it faces different challenges, like battling wild Pokemon or finding hidden treasures.
Well, it could start with Ash being in a new region where Treecko are very rare. He stumbles upon a young Treecko that is being bullied by other Pokémon. Ash steps in to protect it, and Treecko, seeing Ash's kindness, decides to join him. Their journey together focuses on exploring the unique ecosystems of this new region. Treecko has to adapt to new battle styles and opponents. Ash and Treecko also befriend a group of local Pokémon trainers who help them understand the secrets of the region. In the end, they face a powerful trainer who has a team full of strong Pokémon, and they have to use their combined skills and the knowledge they've gained to win the battle.
The 'ash catches treecko fanfic' might focus on the backstory of the Treecko. Perhaps it was a lone Treecko that had been through a lot before Ash came along. The fanfic could describe how Ash sensed its potential and was determined to catch it. It could also include details about the Poké Ball used, the battle (if any) that preceded the catch, and the moment of capture which could be really exciting and full of anticipation.
The plot could involve Treecko being chosen for a special mission in the mystery dungeon. Maybe there is a powerful and ancient artifact hidden deep within the dungeon that has the power to change the balance of the Pokemon world. Treecko, despite being small and not as powerful as some other Pokemon, is selected because of its determination and pure heart. Throughout the story, Treecko has to overcome many obstacles, both physical and mental, to reach the artifact and decide what to do with it.
Well, there's a fanfic where Ash starts with Treecko called 'Treecko's Ascent with Ash'. In this one, Treecko is shown to have unique abilities that Ash helps to develop further. It also delves into how their partnership affects the other Pokémon in Ash's team. There may also be a fanfic that has a more comical take on Ash starting with Treecko, like 'Ash and Treecko's Hilarious Happenings', where they get into all sorts of funny situations during their travels.
One possible plot is that Treecko gets separated from its trainer early on. It then has to find its way back, facing many dangerous Pokemon on the way. During this journey, it learns new skills and becomes more independent.
Pikachu is a very likely candidate. It's Ash's most iconic Pokemon and has a deep bond with him. Whenever Ash is in trouble, Pikachu often steps up to protect him.