Pyukumuku was caught in That New Old Gang of Mine! while Goh and Ash were exploring Melemele Island. Later, Pyukumuku was seen being greeted by Goh's giant Magikarp at Cerise Laboratory.
In All Out, All of the Time!, Pyukumuku was used by Goh to battle a Bruxish that he needed to catch during the Pokémon Catch Adventure Race. Using its Toxic to weaken the Water-type Pokémon, Goh successfully caught it.
In Big Brother to the Rescue!, Pyukumuku became frustrated with the polluted water stream in Cerise Park after it was forced to abandon its favorite spot, and began spreading its slime all over the area to display its unhappiness. However, after the source of the pollution was found, and the water stream was cleared by Suicune, Pyukumuku returned to its favorite spot in the park.
In Heroes Unite!, Pyukumuku joined the rest of Goh's Pokémon at the lab to celebrate their Trainer's return from the last mission of Project Mew. In This Could be the Start of Something Big!, it attended a surprise party hosted by the Lab members commemorating Goh and Ash's departure.
Pyukumuku is quite lonely and reserved, preferring to remain alone in whatever spot it chooses. Despite this, Pyukumuku is loyal towards Goh, following every command without question. Common to its species, Pyukumuku hates being forced out of its favorite spot, and often displays its unhappiness by spraying its slime all over the area. It also showed to dislike being poked, as seen when it retaliates Goh's Raboot by punching it.