Cilan's Stunfisk is the second Pokémon Cilan caught while on his journey with Ash and Iris.
In "Facing Fear With Eyes Wide Open!," as soon as Ash and Oshawott tried to obtain some Remayo Weed from Palpitoad's territory, it shocked them with Thundershock and engaged in battle. It was fished out and caught by Cilan the same time that Ash captured his Palpitoad.
In "The Club Battle Hearts of Fury, Emolga Versus Sawk!," it was used by Cilan in the second round of the Nimbasa Town Club Battle tournament held by the town's Don George. Against Luke's Larvesta, it used its powerful Scald attack to defeat it, but was then knocked out by Flamethrower.
In BW062, it teamed up with Ash's Pikachu to stop the battle between the Kami Trio. Their combination of Thunderbolt and Thundershock stood well, but they were unable to win against them.
In BW069, it was used to battle Skyla's Swanna, but got defeated.