Gockos are multi-colored monsters with fearsome lobster claws who live deep underground on Mongo.
When Flash, Prince Barin and Dr. Hans Zarkov are traveling underground in Barin's Electric mole, a gocko grabs the machine. Flash emerges to fight the beast, but is caught in its giant claw. Barin puts the electric mole in reverse, chopping the gocko to pieces in its motor. ("The Monsters of Mongo")
In the "Flash Gordon (serial)", Flash and Prince Thun run across a gocko in the Tunnel of Terror, as they hurry to stop Ming the Merciless's marriage to Dale Arden. Flash is caught by the gocko in the cliffhanger to "Chapter 102: The Tunnel of Terror", and Thun shoots the monster in "Chapter 103: Captured by Shark Men".