When Brock was a Pokémon Trainer, he caught Pikachu along with various other Pokémon and added Pikachu to his collection. Later, when Brock became a Gym Leader, Pikachu was one of the Pokémon that was displayed in the Pewter Gym, where Pikachu officially made his debut.
After Red drags Clefairy into the Pewter City Gym to face Brock's Onix, the two had learned of Brock's collection and that Clefairy's cousin Pikachu was also a part of it. The news had enraged Clefairy and had given him the courage to face Onix in battle, which Clefairy later wins by drawing his picture onto Onix's tail, causing Onix to chase after its tail and become dizzy, and is finished off as Clefairy smashes a fallen pillar on its head. By winning the battle, Pikachu was granted freedom from Brock's collection and joined Red's team.
After Red got Pikachu from Brock's collection, he went camping with Red and Clefairy. As Red and Clefairy were fighting over a piece of fish that Clefairy was saving for the next day, it went inside Pikachu's mouth and was eaten whole. Clefairy grabbed Pikachu and used him as a fishing rod despite Red warning them not too since Pikachu's electricity could harm the fish. True to Red's word, Pikachu's electricity zapped the whole lake and several fish went flying out.
Pikachu and his cousin, Clefairy
Later, he went chasing after a Mew who took the Moon Stone from Red. Mew led them to an abandoned water mill and the group went inside. Pikachu hopped around a trap door as he found something. Clefairy translated for Pikachu since Red and Green could not understand what he was saying. Red opened the trap door and the group went in the basement. Clefairy and Pikachu went to play an arcade game on the giant computer but Red didn't want them doing so. Clefairy and Pikachu look around the room and notice some dolls there. He gets spooked by Bill who was in the form of a leopard. After Bill was changed back into a human, Pikachu and the group ran away in fear as they found his human form to be hideous.
Pikachu, Red, and Clefairy take a shortcut in Diglett's Cave and arrive in Vermilion City. On the S.S. Anne, he jumped in when Clefairy called him in for help when Lt. Surge's Voltorb kept on electrocuting him. Pikachu countered Voltorb with his own electricity and kept going under Red's support. However, part of the electricity burned Red's house and caused Voltorb to evolve into Electrode. Both Clefairy and Pikachu take a pole on the ship and whack Electrode with it, sending it flying onto some machinery which caused an explosion and destroyed the S.S. Anne.
Pikachu, Red, and Clefairy dealt with a storm in Lavender Town. The trio ran to Blue's mansion to get away from the storm. He and Clefairy unsuccessfully do some scary expressions toward Red. After Clefairy dealt with a Gastly at the mansion, the trio met Blue in the second floor of his mansion. Pikachu watched Clefairy battle his Gengar and then got chased out by Blue along with Red and Clefairy after Clefairy sucked away Gengar in a vacuum.
While Red and the others were lost, Pikachu went in front of a moving truck and lit up his tail. However, it threw the driver off as the glow was too bright and rammed into the group. They arrived in Celadon City after an ambulance dropped them off there at a hospital. While there, Pikachu found a coin on the floor which was from the Celadon Game Corner. He hopped in joy all the way there. Pikachu tried out one of the slots and became successful as he was able to get straight 7's, which earned him tons of coins and attracted the attention of the whole casino, as well as Giovanni and some Team Rocket members. Pikachu tried out Roulette as Clefairy suggested and he bet all of the coins won previously. Pikachu was able to call the number right and earned double the amount that Clefairy bet on. The trio stay in a mansion afterward where a Hitmonlee came by and took Pikachu. Red noticed it and followed him and Team Rocket to a wrestling arena. Team Rocket tied Pikachu up as Clefairy fought Hitmonlee. As Giovanni held out a bomb, Pikachu zapped it with his eyes and Clefairy ate it in one gulp.
Pikachu went to an island with Red and Clefairy after their boat got burnt by Green's Charmander. He met Erika and her Venusaur while on the island and got accused of being part of Team Rocket, in which Pikachu's Trainer denied. When Clefairy battled Venusaur, Pikachu stepped in midway to stop a leaf attack that Venusaur threw at Clefairy. Pikachu used an electric-type to immobilize Venusaur but it had no effect on it. After the battle, Erika still thought the trio was part of Team Rocket until Red convinced her otherwise. Pikachu and the others left the island. He infiltrated Silph Co. along with the group where he found out about Giovanni using a remote control to duplicate Porygon. Pikachu destroyed the remote and the Porygon return to normal.
In The Legendary Pokémon Appears!!, Pikachu and the group went to Seafoam Islands where they get caught by some villagers in a cage. After Red demanded the villagers to free them, Pikachu and the others were freed. Inside the cave of Seafoam Islands, Pikachu thawed Clefairy out during a battle with Articuno. After freeing the frozen people and Pokémon, Pikachu and the group get rewarded by the villagers's Lickitung using its tongue to slap them. Later, Pikachu performs on stage in the No. 1 Pokémon contest in Aim to be the No. 1 Pokémon!!.
Pikachu evolved into a Raichu in Clefairy Finally Evolves?!, but had later devolved back into a Pikachu in the same chapter.
Pikachu continues his travels with Red and Clefairy in Johto.
In Something Happened!! Let's Go After Pikachu!! of the Pokémon Ruby-Sapphire series, Ruby finds Red's Pikachu and wanting one for himself, decides to steal Pikachu away by bribing Clefairy with food and swapping Pikachu with a Poké Ball containing his Treecko. Clefairy panics when Red and his Tyrogue return, and goes to great lengths to try to disguise Treecko as Pikachu and to lie about Pikachu's actual location. While Clefairy leaves to go retrieve Pikachu himself, Treecko tells Red the truth about what really happened, and the other three leave to also get Pikachu back. Clefairy manages to find Ruby's house and distracts him while dressed in a half-woman and half-man disguise. While Ruby is distracted by confusion, Red and Treecko breaks through the house's window and rescues Pikachu from Ruby's possession.
In Pocket Monsters DP, Pikachu goes to the Sinnoh region.
In Pocket Monsters HGSS, Pikachu returns to the Johto region.
Pikachu traveled to the Unova region along with Red and Clefairy where he crashed into a bush. After Pikachu brushed himself off, he noticed some unseen Pokémon and a Patrat told him that he arrived in Unova.
Pikachu went to Kalos with Red and the others.