Raichu is Madoka's second Pokémon she caught prior to The Shocking Bond! and debuted as a Pichu, she briefly mentioned that he was hatched from an egg.
As a Pichu, He is a bit of a crybaby but he is affectionate to Madoka which was shown in the same episode. He was used against Homura's Liepard and won thanks to his Static ability.
In the second season, it finally evolved into Pikachu after trying to protect Madoka from an Ursaring's Hyper Beam, and won thanks to its newly-evolved strength.
As a Pikachu, its personality remains roughly the same except he's no longer a crybaby, he is brave when facing danger and is willing to protect Madoka Kaname from harm.
In I'm Gonna Raichu A Lovesong!, Madoka decided to evolve Pikachu into a Raichu, which he did and evolved into a different form of Raichu. Lillie told Modoka it was an Alolan Raichu.
Pikachu's known moves are Thunderbolt, Iron Tail, Electro Ball, Volt Tackle, and his ability is Static.