In the stock footage from Flash Gordon (1936), shown in this film, as Flash is telling The Clay People about his previous encounter with Emperor Ming, Ming is bald and Dale Arden has blond hair. In this sequel, Ming has "pasted on" hair and Dale is a brunette. It has been reported that Jean Rogers (Dale Arden) had many other film roles pending at that time (1938) that called for her to be a brunette.
Much of the background music was originally used in Bride of Frankenstein (1935). Also, the song that played in the background during the sequence recapping the previous chapter's events was the theme for The Invisible Man (1933).
The serial debuted in March of 1938, just seven months before the infamous Orson Welles' "War of the Worlds" Halloween broadcast. To cash in on the controversy caused by the radio show, the studio edited the serial into a feature film, Mars Attacks the World (1938), and released it to theaters in November of that year.
King Features Syndicate released the three Flash Gordon serials as well as Buck Rogers (1939), Red Barry (1938), Ace Drummond (1938) and other comic strip cliffhangers to US TV in 1951. Because the television show Flash Gordon (1954), starring Steve Holland (I) as Flash, was in syndication in late 1953, the three Universal Pictures "Flash Gordon" theatrical serials were retitled for TV broadcast. Flash Gordon (1936) became "Space Soldiers", Flash Gordon's Trip to Mars (1938) became "Space Soldiers' Trip to Mars" and Flash Gordon Conquers the Universe (1940) became "Space Soldiers Conquer the Universe". To this day both the three original "Flash Gordon" serial titles and the three "Space Soldiers" titles are used.