Apparently, this movie is one of writer Terry Pratchett's favourite movies. Pratchett has said "May I also add that the film 'The Return of Captain Invincible', which is a series of bad moments pasted together with great songs and a budget of fourpence, is also a regularly-viewed video in the Pratchett household."
Sir Christopher Lee singing in this movie was out of the ordinary at the time, but 13 years later, Lee recorded his first album, "Sings Devils, Rogues & Other Villains (From Broadway To Bayreuth And Beyond)", containing a mixture of classical, opera and modern music, followed by the 2006 standards album "Revelation" (including Paul Anka's "My Way"), and the heavy metal concept albums "Charlemagne: By the Sword and the Cross" (2010) and "Charlemagne: The Omens of Death" (2013). Lee also sang in the film The Wicker Man (1973).
Three of the ten songs featured in this movie were from Richard O'Brien and Richard Hartley, the team behind the The Rocky Horror Picture Show (1975) and Shock Treatment (1981).
Publicity for this movie maintained that its special effects were "better than those in Superman (1978)".
This movie's American distributor was Jensen Farley Pictures. Apparently, just a few days before this movie's stateside debut, the company went out of business.