Pikachu

On day one, Pikachu wants nothing to do with Ash: it shocks him, dodges the Poké Ball and only moves when dragged on a rope. Everything changes when a flock of Spearow attacks. Ash shields Pikachu with his own body, and Pikachu, though hurt, unleashes a huge bolt to save him. From then on they're inseparable, and Pikachu rides on his Trainer's shoulder instead of in the ball. It only ever says versions of its own name, "pika" and "pikachu," and everyone still gets what it means.

In episode two, Team Rocket sees its power during a raid on the Viridian City Pokémon Center and decides to steal it. At the Vermilion Gym, Pikachu loses to Lt. Surge's Raichu. Ash offers a Thunder Stone so it can evolve, and Pikachu refuses: it wins the rematch as a Pikachu, using its speed. Later, Ash considers leaving it with a colony of wild Pikachu, and Pikachu chooses to come back to him.

In Mewtwo's fortress, each Pokémon faces its clone. Pikachu refuses to fight its own and just takes the hits without striking back. When Ash throws himself between Mew's and Mewtwo's attacks and is turned to stone, Pikachu tries to wake him with shock after shock until it cries. Its tears and those of every Pokémon bring Ash back.

At the start of Hoenn, a Team Rocket machine overloads Pikachu with electricity and it falls ill. Ash rushes it to a Pokémon Center on May's bike, which Pikachu ends up wrecking, just like Misty's years earlier.

At the Battle Frontier in Kanto, Pikachu masters Volt Tackle, its strongest move: it charges wrapped in electricity and slams into the opponent, taking some of the damage itself.

Ash arrives in Unova and runs into Zekrom in the middle of a storm. The Legendary's lightning leaves Pikachu unable to use its electricity. Still not at full strength, it loses its first battle to the Snivy of Trip, a rookie, and Ash has to restart his journey almost from scratch. Pikachu gets its powers back and leads a whole team of Unova Pokémon.

In Alola, Ash gets a Z-Ring from Tapu Koko, and Pikachu starts using Z-Moves. During the Ultra Guardians' mission to rescue Lusamine, Ash's Z-Crystal turns into Pikashunium Z and Pikachu fires off 10,000,000 Volt Thunderbolt, an even stronger move that's all its own.

In the World Coronation Series, Pikachu gains Gigantamax and reaches the Masters Eight final against Leon, Galar's Champion. The battle ends in a head-on collision between Pikachu and Leon's Charizard, with Pikachu charging wrapped in electricity like the old Volt Tackle. Charizard goes down, and Ash becomes world champion with his day-one partner.

For the farewell, Pikachu travels with Ash, Misty and Brock again and, in the final episode, leaves Pallet Town on Ash's shoulder, down a road picked by tossing a twig into the air.

Pikachu and Clefairy were both considered as the franchise's stars. Pikachu won the anime mascot spot because it was popular with kids and appealed to boys and girls alike, and because picking one of the starters would have left out fans who chose another. Ikue Ōtani has voiced Pikachu in Japanese since the first episode, and that same voice is used in every language so the name sounds the same worldwide.