Gloom debuted in Made for Victory as an Oddish, being used by Leaf to scout out wild Pokémon with its Sweet Scent move. A wild Poliwag appeared which Oddish defeated, allowing for Leaf to capture.
In Perfect Love, Oddish teaches Bulbasaur Sleep Powder off-screen. It appears within the episode to battle against Damian and Ken, putting their Pokémon to sleep.
In Wanted!, Oddish is sent out to put Ken's Electabuzz to sleep, however Electabuzz outpaces Oddish and the Sleep Powder misses.
In Time Heals, Oddish appears battling Team Rocket throughout the episode.
In Corner Royale, Oddish is first sent out to put Team Rocket members to sleep. It's later used alongside Zubat to battle a Team Rocket member's Hitmonchan and Hitmonlee, evolving into a Gloom during the process.
It later cameos in Blind Fury, playing with Poliwag.