The reason the aliens rarely face one another is that the guest actors kept breaking up looking at each other's head-pieces.
During the show's original run, stills from this episode were made into a GAF Viewmaster package.
This episode was coupled with Breakaway (1975) for the TV movie titled Alien Attack (1976), which included newly filmed scenes of the Space Commission headquarters on Earth.
This was reportedly the second-most expensive episode to film out of the entire series (Breakaway (1975) cost the most - between paying off Rudi Gernreich for the costume designs and an aberration in the special effects filming equipment - unnoticed for weeks - costing "thousands and thousands of pounds", according to Gerry Anderson).