For this installment, Roy Thinnes didn't have much screen time. This was due to the actor needing a rest from the grueling production schedule.
One of the last TV appearances for Gene Hackman, as his film career was gaining momentum at this point.
The invaders are seen for perhaps the first and last time as spores growing into "infants" that appear to be slimy, brown-and-green-tinged blobs. They have neck-less heads and each is seen to be forming a pair of stubby arms. Of course, this is only what their young look like.
Gene Hackman plays a character named Jessup. Hackman turned down the role of Colonel Jessup, Jack Nicholson's Oscar nominated role in A Few Good Men (1992), to play his Oscar winning role of Little Bill Daggett in Unforgiven (1992).
Wayne Rogers and John Randolph guest star in this episode. Wayne Rogers went on to play the character Captain "Trapper John" McIntyre on the television series M*A*S*H (1972). John Randolph would later guest star on a couple episodes of the M*A*S*H spin-off Trapper John, M.D. (1979) where "Trapper John" was played by Pernell Roberts.