Azumarill first appeared when it, Vincent's Meganium and Ash's Bulbasaur and Squirtle saw an apple on a tree. Bulbasaur and Meganium used their Vine Whip to fetch the apple, they both pulled to try to get it, but the apple snapped in half so everyone was happy until Azumarill threw the apple at Squirtle thinking it was funny. The latter was about to fight Azumarill until they stopped, but Meganium tripped Bulbasaur and they both started to fight. Luckily, Harrison used his Miltank's Heal Bell to calm all of them down.
Azumarill was used later in the Silver Conference against Ash. It went up against his Pikachu. Azumarill started with Water Gun while Pikachu used Quick Attack. After his attack got avoided, Pikachu use Thunderbolt while Azumarill intercept with Bubble Beam. The latter used Icy Wind to hit the former, followed by an Iron Tail. However, Pikachu was able to grab onto Azumarill's tail and used a super-effective Thunder, defeating the Aqua Mouse Pokémon.