Alternative 3 was a documentary produced in 1977 by Anglia Television in the UK. Originally reporting on the “brain drain” of UK scientists, the documentary crew eventually discovered a secret joint US/USSR space program that had actually landed men on Mars in 1962 in advance of “alternative 3” – a plan to evacuate the Elite from Earth and colonize Mars before Earth succumbs to global warming and eventual environmental collapse (which was going to happen much quicker than folks thought). Some “ordinary folk” would be kidnapped, pacified via mind control, and used as slave labor on the new Martian colonies while the rest of us proles are left behind to wallow in our own filth.
Oh yeah, along the way evidence is discovered of extraterrestrial life.
The whole program was a sham of course – sort of a modern version of of Orson Welles’ War Of The Worlds broadcast but with current (for 1977) production values, “official sounding” presenters, and plenty of “documentation”. The documentary was supposed to air on April 1st 1977, but due to scheduling issues it didn’t air until June. A follow-up book tie-in was published and as they say… hilarity ensued.
Of course, quite a few folks took it seriously and still do. Fortean Times and Wikipedia both have a good rundown of the whole Alternative 3 mythology.