This film, I diafanoidi vengono da Marte (1966), Il pianeta errante (1966) and La Mort vient de la planète Aytin (1967) (the "Gamma One Quadrilogy") were all shot at the same time in order to save money.
While filming, a crack in the pool while filled with "blood" originated a leak, so people in the neighborhood suddenly saw blood-like red-colored water coming out from their taps.
The film is the first of four "Gamma One" science fiction films. The films were originally contracted by Metro-Goldwyn-Mayer to be made for TV movies but were released theatrically instead in some countries.
The painting shown at 1:12:30 is "The Garden of Earthly Delight " by Hieronymus Bosch.
The poor special effects combined with low-budget aesthetics and general cheesy feel of the picture have made it a favorite of bad-movie fans.