Flannery's Magcargo, nicknamed Mag, evolved from one of Flannery's two Slugma.
Mag first appeared in Poetry Commotion when she and Meg, Flannery's other Slugma, accidentally set her hair on fire. When Flannery's Torkoal was stolen by Team Rocket, the young Gym Leader chose Mag to help rescue it. During the battle with Team Rocket, Mag evolved.
During Flannery's Gym battle with Ash, Mag was the first Pokémon she used. Mag put up a good fight against Ash's Corphish, despite severe type disadvantage but was eventually defeated by the Water type.