Thunderbirds is a British mid-1960s science fiction television show devised by Gerry and Sylvia Anderson and made by AP Films using a form of marionette puppetry dubbed "Supermarionation". The series followed the adventures of International Rescue, a secretive organisation created to help those in grave danger using technically advanced equipment and machinery launched from its hidden Tracy Island base. The series focused on the head of the organisation, ex-astronaut Jeff Tracy, and his five sons who piloted the "Thunderbird" machines. Its London agent, Lady Penelope, also featured as a frequent guest-star. Perennially popular, the series has benefited from periodic re-runs since and is still shown today - as well as subsequently inspiring a number of other television programmes and advertisements, theatrical productions, feature films and substantial merchandise.