This was the first episode filmed in color.
Ed Hinton, the actor portraying the "Cave Man" in this episode, died within three days of veteran actor John Hamilton who played the lovably gruff "Perry White", editor of 'The Daily Planet'. Hinton was tragically killed in a plane crash on October 12, 1958. Hamilton died of a heart attack on October 15, 1958.
In "Through The Time Barrier" when the crew are saying goodbye to the cave people, Perry White addresses the cave woman as 'Lana'. (whether that was her real name or not) Lana is the name of Clark Kent's school girlfriend in Smallville.
During the first two seasons the gun they used for the "Faster than a speeding bullet" clip was a Smith and Wesson Model 10 revolver. Starting season three they switched to a Colt Official Police revolver.