The Phantom Planet is a 1961 science fiction film about tiny people battling aliens in outer space. Prepare yourself for the voice-over narration. Is "man" driftwood?
Moria calls it "cheap," "rather dreary and slow moving" and "a frustratingly slight film that fails to go anywhere". Million Monkey Theater compares watching it unfavorably with the suffering endured due to kidney stones. And I've had kidney stones. The plot description is so thorough, though, that reading it can spare you the pain of watching the movie.
1/3/2009: SFSignal features it for their Sunday Cinema viewing.