You will watch Pokemon Season 1 Episode 21 online for free episodes with high quality. Online episode guide, Pokemon Season 1 Episode 21 Bye Bye Butterfree As the group continues on their way, they notice a flock of Butterfree out over the ocean. Brock informs Ash that it is the mating season for all of the Butterfree. Ash decides to release his Butterfree so that it can mate. However, Team Rocket has plans to steal all the Butterfree.