 It was specifically written to exclude scenes from "The Mysterons", to which there are flashbacks in "Winged Assassin", "Dangerous Rendezvous" and "Traitor".The framing scenes were shot on Century 21 Studios' Stage 3 between 22 and 25 November 1967 alongside filming on "The Most Special Agent", the first episode of "Joe 90", on Stage 4.The finished episode contains only eight minutes of original footage, the flashback to "Crater 101" taking up a further eight minutes of the running time.