This is more or less exactly what happened to the Donner Party except obviously not as wacky.

Sherwood Schwartz shamelessly ripping off one of his own shows - formula and characters and all. It amazed me when I first saw the intro for the series awhile back (and tried submitting it for the sheer gall factor of the production) and I believe I may have encountered this hasty stapling together of the first few episodes being passed off as a "movie" being aired somewhere in the hinterlands of cable TV channels years ago.

Ah, the 70s. You always manage to disappoint me in just the right way.