The robots Gog and Magog were operated by little people.
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.
The unusual helicopter seen early in the movie is a McCulloch MC-4C tandem-rotor. Only a handful were built as military prototypes.
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.