In the latest part of our ongoing behind the scenes documentary series,, 'Thunderbirds Unseen', we take an in-depth look at how two episodes were expanded in scope and ambition following the decision that each 'Thunderbirds' episode was to be an hour long. "Perils of Penelope" and "Terror in New York City" are two particularly well regarded episodes of Thunderbirds, with action packed-plots, arresting visuals that continue to enthral audiences after almost six decades, but what were their original storylines? Explore these classic Supermarionation episodes like never before in the company of co-creator Sylvia Anderson and directors David Elliott, Des Saunders, and David Lane. With the help of newly unearthed 35mm film and studio documentation, 'Thunderbirds Unseen' challenges some of the "established" facts of the making of the series' and showcases footage unseen for sixty years. Gerry and Sylvia Anderson's classic television series was a massive success upon its debut in 1965 and