Arbo is an Ekans, a purple serpentine Poison-type Pokémon with yellow underside markings, eyes, and a rattle-tipped tail. It serves as a member of the antagonistic Team Meanies, led by Gengar and including Medicham, directly competing with Team Go-Getters. Team Meanies aggressively pushes aside Team Go-Getters to claim the mission to save Pikachu. At the Kecleon Brothers' shop, Team Meanies empties the supplies, leaving few resources for others, and later confronts and mocks Team Go-Getters. Following Gengar's command, Arbo devours all the Berries collected by Team Go-Getters, hindering their mission and displaying gluttony. Team Meanies deceives Pichu, tricking him into a tunnel; Arbo participates by using Confusion to move a boulder, blocking the exit and trapping Pichu in darkness until his rescue by Team Go-Getters.

After Team Meanies is defeated and injured by Skarmory, Team Go-Getters shares their last Oran Berry to aid them. Arbo initially refuses the offered portion but ultimately accepts after Squirtle argues for mutual assistance among Pokémon. This acceptance suggests a capacity to acknowledge past cruelty. Arbo functions primarily as a follower executing Gengar's commands, utilizing species traits like its tongue to sense the environment. Its role concludes following the joint defeat of Skarmory and the rescue of Pikachu and Pichu.