The four-legged beasts had a long snout with teeth, two eyes, and four fingers. The two-legged beasts, which crawled on their tail-like back end, was short-snouted with teeth, three eyes, and had only two fingers. Both were similar in temperament, roar, and a tendency to assume an upright posture. These creatures were extremely large in comparison to humans, had tough skin that made them resemble rocky mounds when inactive, which allowed them not to register as "living" to Federationsensors.
The animation of these creatures proved to be rather difficult for the animators at Filmation. "The guys that had to animate the rock creatures had a really hard time," storyboard artist Bob Kline recalled. "You could tell from the animation in the show, they were killing themselves trying to keep it consistent on screen." (Star Trek: The Official Guide to the Animated Series, p. 79)