Rod Serling wanted Richard Egan to do the narration because of his rich, deep voice. However, due to strict studio contracts of the time, Egan was unable. Serling said, "It's Richard Egan or no one. It's Richard Egan, or I'll do the thing myself", which is exactly what happened.
Almost all of the men in season one, introduced by Rod Serling's opening narration, were described as being thirty-six years old.
Rod Serling made up the phrase "sixth dimension" to use in season one's opening narration. William Self of CBS asked him what was the fifth dimension (given that dimensions one through three are exemplified by a line, a plane, and a cube, respectively, and the fourth was once thought to be time). Serling answered, "I don't know. Aren't there five?" He then changed the narration to "There is a fifth dimension".
Rod Serling invited viewers to submit a script. He was flooded with over 14,000 scripts, and he actually got around to reading 500 of them. However, only two were any good, and he couldn't use them because they didn't fit the format of the show.
Rod Serling thought he had come up with the term "The Twilight Zone" on his own (he liked the sound of it), but after the show aired, he found out that it is an actual term used by U.S. Air Force pilots when crossing the day and night sides above the world.