Features the famous Chemosphere House. Designed by architect John Lautner, the house is seen in a few exterior shots but the inside shots were on a set designed to resemble the house's interior.
The eye patch in this episode, which covers half of the scalp worn by "Karl Emmet" (Sean McClory), is almost exact to the one worn by "Dr. Leighton" (William Sargent) in the Star Trek episode 'The Conscience of the King' (season 1, episode 13). Both episodes were directed by Gerd Oswald two years apart.
Based on Clifford D. Simak's short story "Good Night, Mr. James" that appeared in the March 1951 issue of Galaxy Science Fiction magazine. In the original story, the creature was called a puudly and the story was later reprinted as "The Night of the Puudly." In 1977, Simak described it as a "vicious story - so vicious that it is the only one of my stories adapted to television." (Simak might have meant American television, because four of his other stories were adapted for the British series "Out of This World" and "Out of the Unknown.")
Henderson James' car appears to be the George Barris Villa Rivera, a 1963 Buick Rivera given to George Barris by Buick. The "car kulture deluxe" website has an interesting write-up and history of the vehicle. As well as being one of George Barris' personal cars, it appeared in "For Those Who Think Young" with James Darrin. According to the website, the car is still around.