Pikachu originally belonged to Eusine in the future. It became a messenger sent from there by Eusine and Bill. After the time travel, it ended up in Gold's hands when he had a battle with Falkner's Articuno. Due to its level being high and recently joining Gold's team, it was not ready to listen to him. During the battle, Pikachu gets assisted by Totodile and Pidgey who also join in. Due to their teamwork, Pikachu was able to win the Gym Battle, thus earning Gold a Zephyr Badge. Since then, Pikachu became his signature Pokémon.
Pikachu participated in a Basketball Tournament where it went up against Firebreather Takeo. Due to its speed and quick movements, Gold was able to win the tournament. Then, it went with Gold to Union Cave when a Lapras caused ruckus there. Pikachu fought the Lapras and managed to put up a great fight. When Gold met Whitney, she was interested in Pikachu and wanted it. As a result, she had a battle with Gold and won, taking Pikachu. She stays with Gold until he got better. While still in Whitney's possession, Pikachu watches Gold fight Black in a tournament using Fighting-type.
Pikachu headbutts some trees in order for berries to fall as various Miltank were getting sick. However, Pineco fell out instead. Pikachu continued to headbutt trees until it found berries which was taken by a Spearow and was returned to the group when Morty's Gengar used Mean Look to prevent the Spearow from getting away. After Whitney's Miltank felt better because of the berries Miltank ate, she rewards Pikachu back to Gold along with the Plain Badge. Pikachu battled with Black's Gyarados in order to determine whether or not the Gyarados should be given to Gold. However, Pikachu was stopped midway by Jasmine and had her Steelix take over. When Gold and the others were in Cianwood City, Pikachu reunited with Eusine in which Eusine reveals the story about Pikachu coming from the future.