The main title sequence, seen on all of the 32 episodes produced for this series, is accompanied by a special voice-over by Ed Bishop, who provided the voice for Captain Blue. This particular voice-over was never again heard on any of the following 31 episodes: 'The finger is on the trigger. About to unleash a force, with terrible powers, beyond the comprehension of man. This force we shall know as, The Mysterons. This man will be our hero, for fate will make him indestructible. His name, Captain Scarlet.' Although this pilot episode does not feature an on-screen title, it has always been recognised via production documentation as The Mysterons
An interesting discovery, found by Chris Bentley (author of The Complete Book of Captain Scarlet), is before the Spectrum patrol car with Captains Scarlet and Brown turns off the highway and crashes into an explosion, the picture colour slowly changes from full colour to a blue 'monotone', which is used to indicate the invisible but watching and witnessing presence of the Mysteron forces. The colour abruptly returns to its previous full-colour, however this type of effect would have been lost during the series' original television broadcast in 1967 in the UK as all 32 episodes during that time were broadcasted in black & white
A stock photograph of New York City is used to visualise the empty, quiet city, for the maximum-security arrival of the World President. The Empire State Building however is seen in this one photograph, and according to Bentley's book, the production documentation filed by the show's producers indicates that Captain Scarlet was set in the same fictional world as Thunderbirds, so therefore that particular building should not be seen, as it was demolished by a destructive earthquake in the 1^st season Thunderbirds episode, Terror in New York City
The director of this episode, Desmond Saunders, took on the role as the Supervising Series Director. He only directed this one episode. Strangely enough, he is credited as 'Des Saunders' under his Supervising Series Director role
Husband and wife team, Gerry & Sylvia Anderson, only wrote the teleplay for this one episode. Gerry remained as the Executive Producer, although he wasn't around that much during the show's production, and Sylvia remained credited only as the show's format developer, along with Gerry

The Spectrum saloon crash seen in the pilot is seen in two different colours: full colour and a blue 'monotone', but in this episode however, the whole sequence, seen in flashback footage where Captain Scarlet recalls his death, remains in full colour
Like Desmond Saunders, the Supervising Series Director and the Director of the pilot, David Lane, who also directed this one episode, was also directing the second motion picture of Gerry Anderson's most popular and cult-trademarked Supermarionation series, Thunderbird 6
This was the first written script for the show by Tony Barwick. He would also write the scripts for 17 more episodes of the series, as he was Script Editor right from the start of the series. Barwick was not new to this type of script-writing as he assisted Thunderbirds Script Editor Alan Pattillo in doubling the length of existing 30-minute scripts. Barwick also wrote the teleplays for two Thunderbirds episodes, both 2^nd seasoners, entitled Lord Parker's 'Oliday and Ricochet

Short, minor scenes from Tony Barwick's original script draft for this episode were either edited out before production of this episode commenced, or the scenes that had been filmed were 'left on the cutting room floor' (didn't make it to the final cut). These scenes would have shown Spectrum consisting of officers code-named 'Yellow' and 'Purple', and would have also shown the Room of Sleep, an area of Cloudbase which is referred to in Treble Cross and Place of the Angels, and actually seen in Place of the Angels

Originally, when Barry Gray, the show's music composer and theme writer, scored this episode, he produced a cue which was intended to be used for this episode; however, it didn't make the final cut. It is used and heard though for the very first time in Place of the Angels
The radio music heard in the garage when Black murders the mechanic was taken from Gerry Anderson's live-action feature-film Crossroads to Crime, produced in 1960

The original shooting script suggested that the live-insert footage of Tiempo's X-Rays being developed might of possibly been shot on location at Wexham Park Hospital – Stoke Green, only a short distance from the Century 21 production studios, but this proved unnecessary
Doctor Magnus's colleague, Doctor Turner, is named after the one of the show's (and this episode's) director, Ken Turner

The scenes involving the disc jockey at TVR-Control, Captain Black engineering the TVR satellite's destruction and the following recreation were late additions written into the script. The original script simply featured the Mysterons using their influence to seize control of the TVR satellite. The TVR-17 disc jockey is named Bob Lynn, named after this episode's director, Robert Lynn
The smiler configured head for Colonel White is used for the first time in this episode, but unfortunately rarely features in following episodes. The second time it is seen, is in the episode Model Spy

This episode is the first in the Official ITC Recommended Broadcasting Order to contain the closing titles and title sequence, accompanied with the 'Captain Scarlet' record track, sung by (no-hit-wonder) 'The Spectrum'. It wasn't, however, the first episode to be produced with this second rendition of the closing titles sequence – Lunarville 7 was.
The Glen Garry Castle was adapted and constructed from the McGregor Castle set, built for the Stingray episode Loch Ness Monster. It also appeared additionally in the 1^st season Thunderbirds episode, 30 Minutes After Noon

According to Chris Bentley's aforementioned book, the original draft script for this episode starts with Scarlet losing all of his money at the casino. However in the final shooting script, additional scenes were inserted, showing Steel and Kramer's motorcar accident down the hillside, their Mysteronised reconstruction, and Colonel White's briefing to the Spectrum officers following the broadcast of the Mysterons' latest threat. The scenes showing Captain Black murdering the Mason's Auto Garage attendant and the Mysteronised attendant sabotaging Steele's car, were added during the later stages of the development of this episode's script
The deserted ranch house, where Captain Scarlet shoots Captain Blue with a stun-gun, to fool Mysteron agents Steele, Kramer and Captain Black, that he really is working for them, is made from using the model of the hunting lodge, seen in Spectrum Strikes Back

In the original drafted script for this episode, the Lunar Controller's speech which starts the actual episode was extensively longer than what made it to the final cut. After saying: "At present, there are some 4,000 people living and working on the lunar surface" (when the camera moves close to the Lunarville 7 complex — the very second shot of the episode), the Controller originally went on to say the following: "Many of us have been here for several years. I myself have lived in Lunarville 7 for the past eight years, and have come to regard the Moon as my home. We were all born on Earth, but I see a future where men will be born, spend all their lives, and die on the Moon. We have now developed our centres to the extent of being self-sufficient, able to support all their inhabitants." This would have helped the viewer answer the rethorical question that Colonel White asks towards the very end of the episode: "We shall never know how the Lunar Controller and his personal aide were taken over by the Mysterons." — eight years is certainly a long enough time to be murdered and resurrected as a Mysteronised life-form

This is the second out of 2 episodes where all 14 regular characters appear in (the other episode being Flight to Atlantica; it is also the only episode where there aren't any guest starring characters.