The robots Gog and Magog were operated by little people.
The unusual helicopter seen early in the movie is a McCulloch MC-4C tandem-rotor. Only a handful were built as military prototypes.
The centrifuge scene was filmed at USC. The actors became sick and were replaced by dummies.
As of April 2005, only one complete dual-projector stereoscopic 3-D print was known to exist anywhere in the world. The left and right prints did not match: the color was severely faded on one side, but the film was still viewable in 3-D. The film was completely restored in 2006 by the 3-D Film Archive, which restored the faded color to the only remaining left-eye print.
Director Herbert L. Strock had very poor vision in one eye and consequently was unable to properly gauge how the 3-D effects were, and had to rely on others to tell him. Coincidentially, André De Toth, who directed House of Wax (1953), arguably the most famous 3-D film, only had one eye and could not see the 3-D effects at all.