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: Throughout the second series there were three 'guest' voice artists: John Tate, Paul Maxwell and Charles Tingwell. Tate had previously voiced numerous characters in episodes during the first series such as 'Sun Probe', whilst Maxwell and Tingwell would appear in the next Gerry Anderson creation 'Captain Scarlet and The Mysterons' as the voices of Captain Grey and Dr Fawn, respectively. None of these artists were credited in the end titles.
Trivia: Although he was a regular character in the first series, the Hood does not appear in any of the six episodes in the second series.
