This movie seems to have been designed to put audiences to sleep. To start with, the prologue, in which international astronauts discover, on the first lunar landing, that Victorian era explorers already walked on the moon, is the best part of the movie. It's downhill from there and it takes an hour or so for the first Harryhausen monster to appear. When it does, it just ambles around and roars and then is dispatched with no drama. Poor acting adds to the film's woes -- Lionel Jeffries should be scolded in particular for his mugging and constant scene-stealing (just watch that man's eyebrows, wow!). Interesting script can't make a good film without any help from cast and crew.
Review of First Men in the Moon
