The living room set is the same one seen in Third from the Sun (1960). It is a redressed version of George's living room from The Time Machine (1960).
Marcusson mentions they have traveled 35 million miles to Mars. The distance between Earth and Mars ranges between 36 million and 250 million miles due to both having slightly elliptical orbits and different lengths of time to orbit the sun.
As in many other episodes several props of Forbidden Planet (1956) are used, especially in the interior of the astronauts' spaceship.
Rod Serling changed a couple of elements from the original source story (Brothers Beyond The Void, by Paul W. Fairman) for this episode. In the original story the protagonist is Marcusson and Conrad is only in the beginning of the story as Marcusson makes the trip to Mars alone. Serling also changed the climactic utterance from the story's mundane "People are the same everywhere," to his more poignant version. It isn't clear why Serling changed the story and made Conrad the protagonist.
In the opening monologue, Mark Marcusson (Paul Comi) is described as 35 years old and Sam Conrad (played by Roddy McDowall) as 31. At the time the episode was released, McDowall was indeed 31 but Comi had just turned 28.