Ash, Pikachu, Misty, and Brock became inseparable after both Misty and Brock left their Gym Leader positions to travel with their new found friends.
The Pokemon anime series had its U.S. debut in 1998, and followed Ash on a Pokemon journey in the first episode as he is introduced to the reluctant Pikachu and tells the tale of their quest to find more Pokemon for battle.
During the adventure, Pikachu finally warms up to Ash and they forge a friendship after an intense battle.
However, the series is 20 years old and more than likely aiming at a whole new audience to rope into Pokemon madness with new merchandise and new characters.