James's Amoonguss first appeared in BW109, debuting along with Jessie's Frillish when Team Rocket attacked Ash and his friends for the first time since their "Operation Tempest" and temporary retreat back to Kanto.
When Ash and friends were helping the rookie Trainer Nonomi to gain some experience, Team Rocket surprised them, sent out their new Pokémon, and used a combination of Mist and Stun Spore on them and their Pokémon, reducing the visibility to almost nothing and paralyzing Iris's Emolga and Cilan's Stunfisk at the same time, thus leaving Ash alone to face Team Rocket with Pikachu. Using the Mist as his advantage, James had Amoonguss use Body Slam, which was strong enough to actually knock Pikachu out. As Ash sent out his Unfezant to blow the Mist away, Team Rocket was close to stealing Pikachu inside of their mecha. However, thanks to the distraction of Nonomi and her Tepig, Pikachu was freed, although Tepig got caught in the process. For a getaway distraction, Team Rocket fired a combination attack of BubbleBeam and Hidden Power, which, much to their surprise, was endured by Unfezant, followed by an Air Cutter and an Aerial Ace to defeat Frillish and Amoonguss, respectively.
Amoonguss reappeared in BW110 where James sent it out after catching Pikachu. It distracted Ash from holding on to his Snivy when she used Vine Whip to grab onto their balloon. It once again battled Unfezant after Axew freed Pikachu with Dragon Rage. Pikachu joined in the battle and tried to finish off Team Rocket but Amoonguss paralyzed him with Stun Spore before the attack completely blasted them off. Amoonguss was taken out along with Frillish by Unfezant which slammed them into Team Rocket's balloon.