Grubbin is a small, insectoid Pokémon. It has a white body with three nubs on either side resembling simple legs. There are two yellow spots on its side. Its head is dominated by two large, yellow mandibles with reddish-orange tips. The rest of its head is brown and has a reddish-orange structure with a yellow rim on top. It has large, black eyes with white pupils.
Grubbin typically lives underground. It uses its jaw as a weapon, a tool for burrowing, and for extracting sap from trees. Additionally, it can create sticky threads, which it shoots from its mouth and uses to swing around as though on suspension wires. It also uses these threads to stop opponents from moving, so it can then grab them in its mandibles, which are strong enough to snap thick tree branches. Even its natural enemies would rather run away than risk getting caught in its mandibles. It loves electricity and can be found near power plants. They can also be found near Electric-type Pokémon, as a means of avoiding attacks from bird-like Pokémon. Rookidee is a natural enemy of Grubbin.