—Original series
During the original series, rookie Trainer Ash Ketchum begins his journey in the Kanto region, leaving his home of Pallet Town with the only starter Pokémon that Professor Oak had left to give: a reluctant and moody Pikachu. Ash’s quest begins in earnest to defeat all of the Gym Leaders and get to the Pokémon League as soon as he has gained Pikachu’s trust, and he is joined by two mentors, Misty and Brock.
—Advanced Generation series
In this series, Ash travels through the Hoenn region in an effort to compete in the Hoenn League there. He is joined not by Misty, who had been his continuous companion for the entirety of the original series, but May, a rookie Trainer from Petalburg City who at first merely wishes to travel. Eventually, she learns of Pokémon Contests and declares herself a Pokémon Coordinator, training to win Ribbons so she can enter the Hoenn Grand Festival. May’s brother, Max, also travels with the group and helps map out routes to take using his PokéNav.
—Diamond & Pearl series
this series begins with Ash Ketchum beginning his journey by himself, this time through the Sinnoh region. His longtime companion Brock eventually rejoins him, as does Dawn, a rookie Pokémon Coordinator from Twinleaf Town who wishes to follow in the footsteps of her mother.
Like what happened in the Advanced Generation series, both Ash and Brock received a change of clothes. As well, a similarity to the previous series is that Ash attempted to travel to Sinnoh with only Pikachu. He was unsuccessful, however, as his recently-caught Aipom insisted on accompanying him.
—Best Wishes series
the Best Wishes series begins with only Ash Ketchum, headed off to the Unova region with his Pikachu, accompanied by a girl by the name of Iris and with one of the first Unova Gym Leaders, Cilan, who is also a Pokémon Connoisseur. As before, Ash receives a change of clothes. For the first time in the entire show, the Team Rocket trio also receive a change of clothes, but later change back to their original outfits.
—XY series
the XY series began with only Ash Ketchum, headed off to a new region with his Pikachu while wearing a new set of clothes. Joining him this time are Serena, a new Trainer who previously met Ash in her childhood; Clemont, an aspiring inventor and scientist who is also the Gym Leader of the Lumiose Gym; and Bonnie, Clemont’s younger sister. Jessie, James and Meowth continue to follow Ash and his friends through the Kalos region, and have gone back to their more traditional methods of capturing Ash’s Pikachu and other Pokémon, although their appearances are less frequent, just like in the Best Wishes series. Jessie’s Wobbuffet returns to her roster. This series also features a series of side story episodes following the adventures of a Trainer named Alain, who is working to find Mega Stones and defeat all Mega-Evolved Pokémon using his Mega Charizard X. In the XY&Z season, Ash and his friends journey continues as their story merges with the plot of the Mega Evolution Specials, with the group becoming involved with the Legendary Pokémon Zygarde and the villainous organization Team Flare.
—Sun & Moon series
Ash Ketchum heads off to a new region, Alola, wearing a new set of clothes with his partner Pikachu. Unlike the five previous series, however, Ash doesn’t travel through the region. Instead, he becomes a student at the Pokémon School on Melemele Island, where he meets his new classmates Lana, Lillie, Mallow, Sophocles, and Kiawe. Ash receives a Z-Ring and takes on the island challenge to get new Z-Crystals and qualify as a Z-Move user. The Sun & Moon series is notable for Ash’s friends not being present in every episode. Also, characters are usually seen keeping their Pokémon out of their Poké Balls in this series.
Pokémon 