It’s been 20 years since Ash Ketchum began his adventure journey across the Pokemon world, he has conquered many different Pokemon and countless titles.
After each trip to the mainland, Ash’s squad gradually `fell apart` and he had to rebuild the squad from scratch.
Charmander, and later Charizard, are definitely the cases that get the most attention from fans.
It was not until after being frozen by the Ice Beam attack in the Orange Islands that the two reconciled and became compatible in battle.
Caterpie is a quite popular Pokemon in the first part of the story.
Bulbasaur was originally the protector of a small village attacked by Team Rocket and was helped by Ash and his teammates.
Pidgeotto, later Pidgeot, is one of Ash’s strongest Pokemon.
Ash’s Aipom is also another interesting case that many people mention.
Squirtle was originally a member of the Squirtle group, a group of nomadic Pokemon that ravaged villages.