Hokey Poké Balls! : Season 7 Episode 34

With Bulbasaur being in May's team, Ash decides to call his own Bulbasaur to meet up. However, Team Rocket has modified the transporting machine, causing them to obtain the Poké Balls that are being transported. While Team Rocket blasts off during the battle, they manage to steal the Poké Balls. Fortunately, Ash's Bulbasaur returns and teams up with May's Bulbasaur to find Team Rocket.