Trivia: There were a lot of changes to the show throughout the second season. Not only was Virgil "re-cast" with both a new head and voice actor (Jeremy Wilkin), but smaller, more lifelike puppet hands were crafted on the marionettes, and the inside of Tracy Island and the Thunderbird crafts were completely redone.
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.