Mechanislave

The Mechanislaves were the spherical robot servants of the sons of Grekk. Several of them were assigned to stand guard over the TARDIS after the First Doctor was captured. When the Doctor and the other prisoners escaped, Deemon reprogrammed the Mechanislaves to attack them, but the Doctor bluffed him into ordering the robots to stand down. Other Mechanislaves threw the TARDIS out a window, but the Doctor was able to get to it in time and dematerialise it before it hit the ground. (PROSE: The Sons of Grekk)

A Mechanislave was among a crowd at Frenko Bazaar, rolling behind a Sycorax. (COMIC: Bazaar Adventures)