For Ash, Pikachu is always a great choice as it's his most loyal and powerful partner. Alongside that, a strong flying type like Charizard could be useful. For Brock, his Onix would be a staple. And perhaps a water - type like Vaporeon could be good for him to balance his team. Since they are teaming up, having a psychic - type like Alakazam could also be beneficial as it can help in battles and also with communication in tricky situations.
Adventure is also quite common. They could go on a journey together that's different from the ones in the original story. Maybe they discover a new region full of unique Pokemon and have to work together to overcome obstacles there. Sometimes, these adventures also involve them helping each other grow as trainers. Another theme is loyalty. Fanfictions might show how Brock is always there for Ash, and vice versa, no matter what difficulties they encounter, like when Ash is in a tough battle and Brock provides crucial support.
In this fanfiction, it could be a mysterious figure who has been secretly observing Ash and Brock all along. This figure might be from an ancient Pokemon - worshipping cult. They betray Ash and Brock because they see their presence as a threat to their long - held beliefs and practices regarding Pokemon. They might use underhanded tactics like stealing their Pokemon or spreading lies to turn the Pokemon community against them.
Friendship is a very common theme. Brock and Ash have a strong bond in the Pokemon series, and fanfictions often explore and expand on that. Another common theme is growth, both as trainers and as individuals.
A popular one is 'Ash and Brock: A Different Path'. In this fanfiction, they go off on an unexpected adventure that tests their friendship. It's full of action and also some heart - warming moments as they rely on each other to get through tough situations.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. These platforms have a wide range of fan - made stories, including Pokemon Ash x Brock fanfictions. Just use the search bar and type in 'Pokemon Ash x Brock' and you'll get a list of relevant stories.
One possible plot could be that within the fanfiction world, there is a new character introduced who seems to be a great ally at first. This character gains the trust of Ash and Brock over time. However, this new character has a hidden agenda. They might be from a rival region and their goal is to undermine Ash and Brock's reputation in the Pokemon world. So they start spreading false rumors about them and turn other trainers against them, thus betraying their new - found friendship.
One great fanfiction is 'Brock and Misty's Adventure'. It beautifully portrays their relationship growth. It has them going on a journey together, facing challenges side by side. Another one is 'Brock and Misty: Unlikely Allies'. In this, they start off not getting along but gradually become closer through various events. And there's also 'The Brock - Misty Bond' which focuses on how their bond deepens over time as they travel through the Pokemon world.
Well, a plot could be that Ash and Brock discover an ancient Pokemon artifact that has the power to temporarily boost a Pokemon's strength exponentially. However, a villainous team also wants it. So they have to protect it while also trying to understand its true nature. Or, they could be on a journey to a far - off island where a rare type of Pokemon lives, but on the way, they face all sorts of challenges like bad weather and other trainers who are also after the same Pokemon. Also, a story where they meet a young trainer who is very much like Ash was when he started, and they take it upon themselves to mentor the kid.
There's a fanfiction called 'Brock and Ash: Unseen Bonds'. In this one, it focuses on the quieter moments between them. It shows Brock being a mentor to Ash in ways that are not always obvious during their regular adventures. It also has some interesting side - stories about the Pokemon they encounter along the way.