The television relay tower (featured in the episode "Edge of Impact") is seen to be owned by British Telecommunications Ltd. The use of this company name in the series pre-dated the formation of the real-life British Telecommunications plc (or BT) by nearly twenty years.
It was while the Round House (through which Thunderbird 3 would be launched) that Derek Meddings realized that the design of the building was just right for Thunderbird 5, the International Rescue space station. Unable to come up with a convincing design before now, this was the last of the five Thunderbird craft that he created. By adding aerials and transmitters to the Round House, he developed the series' most unusual and effective vehicle, although it was to play only a minor part in the finished program.
The episode "Security Hazard" features extensive flashback footage from "End of the Road", "Sun Probe", "Trapped in the Sky" and "Day of Disaster" - so extensive, in fact, that it contains only around ten minutes of new material. The episode was made because the previous two episodes, "Attack of The Alligators" and "The Cham-Cham," had gone over budget and a flashback episode was needed to finish the show's first season. These particular episodes were specifically chosen as, having originally been filmed as half-hour episodes, writer Alan Pattillo knew that the stories could be more easily condensed down to about ten minutes each.
Only two episodes were made in which Virgil's vehicle, Thunderbird Two, was not involved in the story's primary rescue - "Terror In New York City" and "The Imposters". "Terror In NYC"'s non-use of Thunderbird Two was forced because the episode was originally made as a half-hour show; when Sir Lew Grade of ITC demanded the series be remade in one-hour format, AP Films had writer Alan Fennell write in the subplot where Thunderbird Two is mistaken for an enemy bomber and attacked by a US warship; ironically, this helped make the episode the one most fondly remembered by original fans of the show. It also explains why this episode needed two directors (David Elliott and David Lane).
Three Thunderbirds story scripts originally owned by Alan Pattillo ("The Cham-Cham", "Give Or Take A Million" and "Alias Mr. Hackenbacker"), were sold at auction in Melbourne, Australia, for AU$150.00 each on 12 August 1990.
The opening and closing credits of the first episode ("Trapped In The Sky") differ entirely from the rest of the series: the music arrangements are slightly different (in the closing credits, for example, the music for Thunderbird 1's first launch is used); sound effects are used in the montage (including Kyrano's scream); the Mole is not used as a standard picture in the closing credits. It is the only episode where Gerry Anderson and Sylvia Anderson are credited for writing an episode of the show.
In the episode "Trapped In The Sky", Alan Tracy's voice is completely different from all the other episodes that he appears in. In his single short line of dialog, he is voiced by Ray Barrett, although Matt Zimmerman (who did Alan's voice for the rest of the series) is credited in the closing titles (Zimmerman had not yet been asked to do Alan Tracy's voice).
Some of the guest characters were named after real people. For example: Lt. Bob Meddings (seen in the episodes "Trapped In The Sky") was named after Art Director Bob Bell and visual effects supervisor Derek Meddings. Dr. Korda (seen in the episode "Day Of Disaster") was named after Hungarian-born film producer/director Sir Alexander Korda; Lady Penelope's alter ego Wanda Lamour (from the episode "The Cham-Cham") was named after puppeteer Wanda Brown (née Wanda Webb).
The music accompanying the journey of the Martian Space Probe in the episode "Day of Disaster" is entitled "The March of the Oysters". Originally composed by Barry Gray for the Stingray (1964) episode "Secret of the Giant Oyster", the piece is also heard in "30 Minutes After Noon", "The Impostors" and "The Cham-Cham".
In the episode "The Mighty Atom", the teletype printout gives the date on which the atomic cloud is blown away from Melbourne as 6 October and it is then stated that the explosion at the plant took place the previous Monday. If this is 2064, the explosion therefore occurred on 29 September. It is also stated in this episode that International Rescue were not operating when the Australian plant exploded in 2064.
The Hood has never been referred to by any name on all but two episodes - "Martian Invasion", where he calls himself Agent 79 in his transmissions to General X, and "Edge Of Impact", where he gives his codename as "671" when he contacts General Bron. "Edge of Impact" is also the only episode in which we see the Hood acting with motives not involving International Rescue.
Before recording for the second season was due to commence, David Holliday, the original voice of Virgil, had relocated to the United States, so Jeremy Wilkin replaced Holliday as the voice of Virgil for the second season and the two Thunderbirds movies Thunderbirds Are GO (1966) and Thunderbird 6 (1968).
The Thunderbirds' radio code "F-A-B", meaning "message received and understood", didn't stand for anything, it was just supposed to sound "hip". In fact, when asked what it stood for, Gerry Anderson once replied, with some bemusement, "Fab," as though it were obvious. Later, due in part to fan-submitted stories, F-A-B came to mean Fully Advised and Briefed, in keeping with P-W-O-R (Proceeding With Orders Received), a similar radio confirmation code in the series Stingray.
John Tracy's character design and mannerisms were a slightly altered redesign of Lt. Fisher from Stingray (1964). Gerry Anderson claims to have disliked the character's "all-American" quality, among numerous other reasons he has cited over the years, which is why John is so rarely seen in the series.
When the launch sequence of Thunderbird 2 was shot, pilot Virgil Tracy was shown being taken to the craft in civilian clothing. When the completed sequence was cut together, he was seen to have mysteriously gained a uniform. To provide continuity, a scene was later shot and added showing his uniform appearing in the cockpit.
According to "Guinness World Records 2008", the character of Jeff Tracy holds the record for the "Highest Earning TV Character", said to be worth an estimated $US50 billion; assets included maintenance of Tracy Island, all the Thunderbird machines, and so on.
In "The Duchess Assignment", the Duchess of Royston was based on the distinguished British stage actress 'Dame Edith Evans (I)', best known for her role as Lady Bracknell in the film version of Oscar Wilde's novel, The Importance of Being Earnest (1952). This is reinforced by Ray Barrett's marvelous voice for the character, which understandably had the rest of the cast in stitches at the recording session.
The trivia item below may give away important plot points.
By the finale of the series and film "Thunderbird 6," Lady Penelope has lost both her famous car and her yacht. Parker gambled away FAB 2 in "The Man From MI 5", and FAB 1 was destroyed in the crash of Skyship One at the end of the second feature film Thunderbird 6 (1968).