During the USS Enterprise's second visit to the Shore Leave Planet, such a vehicle was lured into taking Mr. Spock into the planet's underground complex, in an attempt to rescue Uhura, who herself was captured by one such hovercraft. Upon viewing the hovercraft in operation, Sulu likened it to "a mechanical nursemaid." (TAS: "Once Upon a Planet")
The name "robot hovercraft" was derived from the episode's script, described as being "a small metallic hover-craft [sic] roughly three feet high. It sports six mechanical arms that can extend and retract and is ringed with electronic lenses or "eyes"." It is further described as being "roughly the size of an oval coffee table."
The novelization of "Once Upon a Planet" (as published in Star Trek Log 3) described much of the information presented in the script notes, stating that this type of hovercraft as metallic, "about a meter high and long," "[not] much bigger than a coffee table," with six mechanical, metal arms, antennae and ringed with electronic lenses.