Beam Me Up, Scotty!: The popular "Submitted for your approval" occurs in the opening monologue just three times. In contrast "In just a moment" occurs in the opening monologue 25 times, which makes this the most said four-word phrase that doesn't include "Twilight Zone". "In a moment" also occurs quite often.
Creator Backlash: Richard Matheson didn't like how some of his episodes turned out (like "Young Man's Fancy" and, surprisingly given how highly regarded it is, "The Invaders"). Rod Serling also admitted that several of the episodes - including some of his own - could have been better ("I guess a third of the shows are pretty damned good. Another third are passable. Another third are dogs").
Matheson did prefer the Twilight Zone adaptation of his short story "Long Distance Call" (titled on the show as Night Call) over his original story, as he felt the original ending was too flat, and the ending created for the Twilight Zone episode added more emotion and depth. That said, many fans actually prefer the original story's ending, finding it much creepier, and find the ending to Night Call too tacky.
The Danza: Burt Mustin as Burt the Bum in "Night of the Meek".
Dueling Shows: With The Outer Limits during 1963-64, the only season both series were in production. While the original Twilight Zone did much better than Outer Limits, and is better remembered in popular culture, neither of its revivals lasted as long as the 1990s revival of Outer Limits.
Edited for Syndication: The Christmas Episode "The Night of the Meek" features a holiday greeting from Serling at the end of his wrap up narration that was generally edited out. Also the fourth season hour long episodes were generally ignored until the Sci Fi Channel started running the show. Between the sixties and the nighties they were mainly shown only as edited together two-hour "movie" specials.
June Foray played the Talking Tina doll in "Living Doll", essentially reprising the voice she did for the real life Chatty Cathy. She also dubbed over a child actor's voice in "The Bewitchin' Pool" using her Rocky voice.
If Kaa wasn't creepy enough, the creepy TV repairman in "What's in the Box" also has Winnie's voice.
On a related, but somewhat more pleasant note, John Fiedler (the voice of Piglet) appears as the mall owner in "Night of the Meek", as well as a subordinate angel in "Cavender is Coming".
Bob Crane, at the time an L.A. disc jockey, provided the voice of one on the radio in "Static".
Lex Luthor was in "Cavender is Coming" and Sinestro was in "People Are Alike All Over" and "Ring-A-Ding Girl".
Quite a few people from Batman were in the series prior to the show:
The Penguin starred in "Time Enough At Last" as the meek Henry Bemis, "Mr. Dingle the Strong" as the titular meek character, "The Obsolete Man" as Romney Wordsworth, a librarian slated for execution for being well just read the title and "Printers Devil" as the devil himself, giving him the most starring roles on the show.
Alfred was in "Passage of The Lady Anne".
Police Cheif O'Hara was in "Nick of Time" as a mechanic, "The Grave" and "Ceasar and Me" as a pawnbroker.
The Mad Hatter was in "Escape Clause" as the Devil.
Catwoman was a very sexy she-devil, in fact being the only female portrayal of the devil in this series in "Of Late I Think of Cliffordville".
The Bookworm was in "People Are Alike All Over".
The Archer was Santa Claus in "The Night of the Meek".
Shame was in "A Hundred Yards Over the Rim" and "The Dummy".
Dr. Cassandra Spellcraft was in "The Sixteen-Millimeter Shrine" as an aging film star longing to recapture her glory.
Jack Klugman a.k.a. Dr. R. Quincy M.E.,Oscar Madison, and Juror #5 starred in "A Passage for Trumpet" "A Game of Pool", "Death Ship" and "In Praise of Pip" giving him the most starring roles in the series tying only with Burgess Meredith.
California Charlie was in "A Passage for Trumpet", "The Odyssey of Flight 33", "Of Late I think of Cliffordville" and "The Old Man and the Cave".
Sarah Onedin was in "A Passage for Trumpet" and "Death Ship".
Bill Mumy a.k.a. Will Robinson and Lennier was in "Long Distance Call", most famously "It's a Good Life" as Goo Goo Godlike Anthony Freemont whom he later reprised in the 2003 series as an adult and "In Praise of Pip".
Nick Fury was in "Long Distance Call" and "The Parallel".
Marathon Running: A long-standing tradition on the Sci Fi Channel (now Syfy) is to air three-day-long Twilight Zone marathons over holidays like New Year's and the Fourth of July.
Reality Subtext: In "The Encounter", where a racist WWII veteran and a young Japanese man (played by George Takei) are trapped in an attic: Takei spent three years of his childhood in U.S. Japanese-American relocation centers, during the war. His impassioned performance is definitely informed by that experience.
Recycled Script: Kept to a minimum for an anthology show. When it does happen, you'll frequently find that the moral of the story is a Family-Unfriendly Aesop version of the previous episode's moral.
"Steel" was adapted into a feature film. Though it's somewhat subverted, as Real Steel, despite being based on the same story as "Steel," bears almost no resemblance to the story (outside of robot boxers). Additionally, the film is decisively more optimistic than the original story's dystopian setting.
The Other Marty: A tragic example in "The Mighty Casey" - Paul Douglas was originally cast as manager Mouth McGarry, but in the rushes he looked like he was drunk. It turned out he looked like he was dying... because he was (he passed away from heart disease after shooting was completed). His scenes in the episode were reshot, with Jack Warden playing McGarry, at Serling's expense.
In the original script for "A Game Of Pool," Jesse Cardiff loses to Fats Brown, but he doesn't die and he immediately begins practicing for a rematch
Orson Welles was originally planned to be the narrator but was too expensive.
According to the book The Twilight Zone Companian, the writer of the episode "A Nice Place to Visit" wanted Serling to play the main character, a petty criminal who dies and goes to what he thinks in Heaven. Serling laughed off the idea and the part went to Larry Blyden instead.
Write What You Know: Many episodes took place in Upstate New York, where Rod Serling was from. Similarly, Serling was a vet of WWII (as were many of the other writers), which led to many a episode.