A pitch for a one-hour television drama grew so large on paper that the treatment ran to 194 pages, enough for a three-hour feature. Sylvia Anderson decided the premise was too good for the small screen, and the project became a feature film instead.

DOPPELGÄNGER (1969), also released as Journey to the Far Side of the Sun, came from Gerry and Sylvia Anderson, better known for their Supermarionation puppet series, making their move into live-action feature filmmaking.

Gerry's idea began with a simple question: what if there were another planet directly opposite Earth, orbiting the sun at the same speed, invisible because it was always hidden behind the star. That notion became a mirrored Earth, complete with a mirrored version of everything on it.

Robert Parrish directed, with a screenplay by the Andersons and Donald James developed from a treatment the Andersons had written with Tony Williamson. The film follows an astronaut, played by Roy Thinnes, and a scientist, played by Ian Hendry, sent by a European space council to reach this hidden planet. Patrick Wymark plays the head of the council and Herbert Lom a double agent feeding their findings to the other side. What the astronauts find upon arrival unravels their understanding of where they actually are.

Barry Gray's score and Derek Meddings' effects work give the film a scale far beyond its television origins, a genuine oddity from a studio known for marionettes.