Audiences got their first look at the crystalline Krotons as they battled Patrick Troughton's Second Doctor in their eponymous four-part story, first broadcast from December 1968 to January 1969. Due to the highly unfortunate fact that, at the time, it was the only complete four-parter left in the archives for the Second Doctor, it wound up being repeated on the Beeb in 1981, bringing the unsteady-on-their-feet foes to the attention of a whole new generation of fans. If only Tomb of the Cybermen had been recovered sooner... There's not much wrong with the ideas behind these Bob Holmes-scripted villains, it's only the execution of the costumes that falls short (the Krotons are actually really good in the Eighth Doctor novel Alien Bodies by Lawrence Miles, where visuals are not a problem). When the Krotons are standing still and viewed close up, they look like the crystals they're supposed to be, and their spinning heads are certainly fun. But when they're called on to move a bit, well... that's when the problems start. Doctor Who foes are often slow (mainly because the monster operators can't see well enough out of the costumes to move normally!), but the Krotons take it to a whole new level. Oh dear.