Processed in old-fashioned 3-strip Technicolor (director Richard Haines had to take the film stock all the way to China where one of the few remaining Technicolor labs can be found) and featuring plenty of inside jokes for film buffs, Space Avenger pays gory tribute to 1950s B-movies. Though primarily a sci-fi films, the plot draws from a variety of the era's popular low-budget genres including violent gangster films and exploitation outings. The story centers on a pair of alien fugitives who crash land on Earth after escaping from an intergalactic prison. Resembling big slimy iguanas, they disguise themselves by leaping into the bodies of human teenagers so they can head off to search for the materials needed to fix their ship. Quickly discovered that Americans in the 1930s lack the technology they need, so the vile creatures return to their ship to hibernate until human technology advances. Fifty years pass. Construction workers are digging a basement for a new building when they inadvertently unearth the spacecraft. The aliens are not terribly pleased and so embark upon a terrible killing spree.
~ Sandra Brennan, All Movie Guide