A Rumble Bug is a small, beetleish creature in that lives in the "Cave of the Rumble Bugs." Rumble Bugs can vocalize a humming sound as well as produce a sound similar to that of a kazoo. Both Rumble Bugs and The Rumble Bug Hum are featured in the Fraggle Rock episode "All Work and All Play."

The Rumble Bugs themselves were seen again 3 years after Fraggle Rock ended as background characters in The Song of the Cloud Forest.