The Rock Giant is a drummer who appears in "Five More Short Graybles." He directs (then physically carries) Marceline to Wizard Bill's music store. He is seen playing the drums when Marceline first encounters him. He never speaks, but he evidently understands Marceline when she asks for directions. He points to Wizard Bill's music store with such force that, when his finger bursts through the door, guitars hanging from the ceiling fall to the floor in a heap, much to Wizard Bill's annoyance.
He has three eyes and only one visible tooth protruding from his permanent frown. Grass covers his back, shoulders, chest, and the top of his head. A blue bird is perched on the small copse of evergreens growing on his left shoulder, and a rabbit, bull moose, and ram are seen standing on his head and shoulders.