The Clangers is one of the finest kids shows made in the UK. It's one of the many works of Oliver Postgate, the creative genius responsible for several generations of happy delighted children.
This is the second episode of the second series and was first broadcast on the 25th of April 1971. It's an unusal episode in as much as it features a human visitor to the Clangers moon where as previous visitors have been far more surreal; Froglets, the Iron Chicken and of course the Soup Dragon, to name but a few.
It's also of interest as the episode watched by The Master in the Doctor Who story; The Sea Devils, just a year later.