Trivia: At the beginning of the episode, when Jeff and Nicky are relaxing at Tracy Island, you can see models of Thunderbirds 1, 2, 3 and 4 on the table. These models were commercially available at the time of the episode's initial broadcast and were produced by J. Rosenthal (Toys) Ltd. Thunderbird 5 is not on the table as Rosenthal's model did not look like the genuine article.
Trivia: Throughout the second series there were three 'guest' voice artists: John Tate, Paul Maxwell and Charles Tingwell. Tate had previously voiced Solarnaut Camp in the episode 'Sun Probe' in the first series, whilst Maxwell and Tingwell would appear in the next Gerry Anderson creation 'Captain Scarlet & The Mysterons' as the voices of Captain Grey and Dr Fawn, respectively. None of these artists were credited in the end titles.
Trivia: In this episode, Alan Tracy's voice is completely different from the one heard for the rest of the series. In his single, short line of dialogue, Alan is voiced by Ray Barrett, as Matt Zimmerman had not been employed when voice recording commenced (although he is credited in the end titles).
Trivia: International Rescue's headquarters was never actually referred to as "Tracy Island" throughout the whole series.
Trivia: This episode features extensive flashback footage from "End of the Road", "Sun Probe", "Trapped in the Sky" and "Day of Disaster", and only 17 minutes of new material. The reason for this is because the previous two episodes, "Attack of the Alligators" and "The Cham-Cham" had gone over budget and a flashback episode was required to finish the show's first season.