The shimmering Galaxy Being effect was achieved by filming actor William Douglas in a brown rubber alien outfit which was coated with glycerin to reflect the hot lights shone against it. In post-production, this footage was negative-reversed and then superimposed onto the main footage. The net effect was one of the most economical but effective aliens in film or television.
Cliff Robertson (Alan Maxwell) later played Theodore Harris in Joyride (1999). Along with Leonard Nimoy, David McCallum, Barbara Rush and Peter Breck, he is one of only five actors to appear in both The Outer Limits (1963) and The Outer Limits (1995).
The Galaxy Being states that he is transmitting from a star system in the NW quadrant of the Andromeda galaxy that has 31 planets.
In Joyride (1999), Theodore Harris (Cliff Robertson / G. Patrick Currie) encountered the aliens while aboard the Aspire 7 on September 16, 1963, the same day that this episode was first broadcast. Robertson plays the protagonist, Alan Maxwell, on this occasion.