Writing and design "The Mysterons" was written by the husband-and-wife team of Gerry and Sylvia Anderson, assisted by series script editor
Tony Barwick. The Andersons devised the formats and characters of each Supermarionation series and usually wrote the first episode, which was often referred to as the "pilot". The appearance of the
Zero-X Martian Exploration Vehicle, first seen in
Thunderbirds Are Go (1966), was intended to mark the transition from APF's previous series,
Thunderbirds, which is set in the same fictional world as
Captain Scarlet. The "pilot" script, written in August 1966, contained several key differences from the finished episode. For example, it elaborated on Captain Scarlet's new Mysteron nature, stating that the reconstruction is a "mechanical man" rather than true flesh and blood. Other differences included a longer Cloudbase introduction, in which the Angels are launched but subsequent dialogue reveals that this is a drill (in the finished episode, only the launch is shown); an additional scene in which Symphony and Melody Angels watch from the Cloudbase
promenade deck as the Spectrum jet takes off; Captain Blue converting the SPV's removable power unit into a personal rotorcraft, or "minicopter", to take on Scarlet (in the finished episode, he wears a jet pack instead); and an additional line of dialogue stating that the original Helicopter A42 crashed half an hour before its reconstruction attacked Blue. Between pre-production and filming, the approach to voice casting changed. It was originally intended that each episode would feature a "guest star" character voiced by a well-known actor. In the case of the first episode, the World President was to have been voiced by an artist "of the
Patrick McGoohan calibre". As special effects supervisor
Derek Meddings was busy working on
Thunderbird 6, his designs for "The Mysterons" were limited to the Spectrum vehicles that he expected to appear in more than one episode: Cloudbase, the Angel Interceptors and the SPV. Understanding that the patrol car, Maximum Security Vehicle, passenger jet and helicopter were to be guest vehicles, he delegated the task of designing these to his assistant
Mike Trim. The pilot script gave few specifications for the car, jet and helicopter. The car, for example, was described simply as a "modern American
saloon car". According to Trim, Gerry Anderson had not intended the Car-Vu to look so futuristic, thinking that it would be somewhat reminiscent of the
Eiffel Tower instead.
Filming and post-production After two months of pre-production, and the renaming of APF to "Century 21 Productions" in December 1966, effects filming began on 2 January 1967 followed by the puppet filming on 16 January. Although "The Mysterons" was the only episode of
Captain Scarlet to be directed by
Desmond Saunders, he would continue to serve as "supervising" director for the remainder of the seriesin part, to guide the new crop of directors that Century 21 had recruited to work on
Captain Scarlet.
Zero-X astronauts Lieutenant Dean and Navigator Conway were originally played by puppets different from those seen in the finished episode; the MEV scenes were re-shot with another pair of marionettes after it was decided that the original Dean, which had a black wig, could be mistaken for Captain Scarlet. Because the Maximum Security Building explosion was an important effects sequence, the scale model was carefully designed and built with the effects team paying particular attention to the interiors, as it was thought that miniatures lacking internal detail looked less realistic when blown up. Besides packing the model with
fuller's earth to create a dust cloud, the team even added miniature tables and chairs. In the end, however, Meddings and Trim believed that such a large amount of dust was produced that hardly any of this special construction was evident on screen. According to Meddings: "We spent hours furnishing miniature rooms – actually plastic tool box drawers – but when we eventually set off the explosives they created so much dust that we couldn't see a thing, so our efforts were completely wasted." To create the blurred, otherworldly look of the Mysteron city, a sheet of glass was placed between the camera and the set; the crew then smeared
Vaseline onto various portions of the glass to distort the lighting. A scene in which Captain Brown and the President are scanned for concealed weapons while travelling down a moving walkway was especially difficult to film as the puppet operators on the bridge above the set had to synchronise their movements with the conveyor belt beneath them. The complicated model shots of Blue's SPV travelling up the Car-Vu's spiral road were simplified by rotating the set rather than the SPV itself, thus eliminating the need move the camera or pull the model on wires. As the wired Helicopter A42 model could not easily be filmed right side up due to its spinning blades, it was upended and flown on wires attached to its underside; the footage was then horizontally
flipped in post-production. The scene of Blue shooting Scarlet includes a
reaction shot that required the brief appearance of a "grimacing" Scarlet head, which was sculpted especially for this episode. Meddings said that the sequence of the Car-Vu's destruction was among the most complex that he and his team created on any of the Anderson productions, and therefore needed extensive planning. In a DVD
audio commentary, Gerry Anderson recalled that as "The Mysterons" was the first episode to be filmed, "everything had to be perfect" on a technical level. The
incidental music was performed by a 16-member band and recorded by series composer
Barry Gray during a four-hour studio session held on 16 March 1967. The opening shot presents a caption that reads "Mars2068 A.D." Although some sources regard this as the title caption, all production documentation names the episode "The Mysterons". Chris Bentley rejects "Mars2068 A.D." as the title, noting that the title captions in later episodes use a different version of the series' customary
Microgramma font. ==Broadcast==