Grumlo is a member and co-ruler of the Gorilla Tribe.
Grumlo is the co-ruler of his tribe, along with Gorzan. Grumlo is more of a spiritual and philosophical leader, and he loves to chill out and go with the vibes. Grumlo leads the tribe in many yoga sessions in hopes of achieving the Great Mellow.
Grumlo appears in the webisode called Vibe of the Mellow Head Dude. He takes G'loona home after she runs around in Gorzan's mech. Grumlo criticizes the Ravens for littering, although the mess was not their fault.
In Gorillas Gone Wild, he leads the tribe in yoga and meditation atop the Tower Flower, but then leads them into battle when Cragger cuts it down, though Gorzan seems to take charge later. When trying to get into the Crocodile Hideout, Grumlo's mech got stuck between the jaws of the Croc base's entrance, almost crushing him and the mech. Luckily, Gorzan saved him.
Grumlo can be seen in other episodes at races and battles, but with no major role in the plot. At one point, he argues with Balkar about cheating in the episode Foxtrot. Grumlo threatens to crush the Bears, becoming strangely violent for such a mellow dude. He also goes to the meeting at the Lion Temple with the other tribe leaders to decide if they will rescue the Crocs from the Wolves.
Grumlo has grey and white fur, suggesting that he is older than the other Gorillas. He wears a sash and a necklace decorated with leaves and petals. His weapon in the sets is a hammer.