A new element introduced in the Galar region from Pokémon Sword & Shield has raised doubts about whether Ash’s Pikachu can evolve in the Pokémon anime. The Pokémon from Pokémon Red and Blue tend to receive a lot of attention when new gameplay elements are introduced, and Pikachu is no exception.
Pokémon from the Kanto region were heavily represented in Mega Evolutions, Z-Moves, Alolan forms, and Galarian forms. Pikachu received a Z-Move, but it didn’t get any new forms. There are special cap-wearing Pikachu that have been released as part of events, but the only difference is a hat on their head. This is due to the fact that Pikachu is the mascot of the Pokémon series and The Pokémon Company likely doesn’t want to dilute its appeal with multiple forms that alter the design.
Pokémon Sword & Shield introduced the concept of Dynamaxing and Gigantamaxing to the series. It’s possible for Pokémon to transform into giants when battling in special arenas. This is called Dynamaxing and it only lasts for three turns, but it grants a huge stat boost and gives access to unique attacks. There are some Pokémon that change form when Dynamaxing, which is known as Gigantamaxing. A lot of Pokémon from Pokémon Red and Blue received Gigantamax forms. Pikachu gained a Gigantamax form that resembled the chubby design which was used in the original Pokémon games.
In the Pokémon Journeys series of the anime, it’s revealed that Ash’s Pikachu has access to its Gigantamax form. This is referred to as the Gigantamax Factor in the Pokémon video games. One important thing to note about the Gigantamax Factor is that it prevents certain Pokémon from evolving. If an Eevee, Meowth, or Pikachu possesses the Gigantamax Factor, then they are unable to evolve. If the Pokémon anime follows the rules of the games (and it generally doesn’t) then Pikachu is unable to evolve in its current form. The same is also true of Meowth from Team Rocket, as it also possesses the Gigantamax Factor.
While Ash’s Pikachu might not be able to evolve in its current form, there is a way to remove its Gigantamax Factor. It’s possible to brew Max Soup in the Isle of Armor, which can activate the Gigantamax Factor in a Pokémon that doesn’t already possess one. This is how the player can grant a Gigantamax form to their starter Pokémon. Max Soup also has the ability to remove the Gigantamax Factor, allowing a player to evolve a Gigantamax Eevee, Pikachu, or Meowth. If the Pokémon anime is following the rules of the games, then Ash’s Pikachu currently cannot evolve into Raichu, but it potentially can in the future if they travel to the Isle of Armor and eat the Max Soup.