When is National Twilight Zone Day? Well, today, May 11, actually. But now you’re likely asking yourself, “What is National Twilight Zone Day?” Well, it’s a day celebrating the famous TV show from creator Rod Serling that aired from 1959 to 1964, with later revival series running from 1985 to 1989 and 2002 to 2003. The day, a relatively new, unofficial holiday, is dedicated to fans showing their love for the series and its mix of sci-fi, horror, drama, and more.

But much like the stories that made up the series, information about what went into the show is “vast as space and as timeless as infinity.” Rod Serling poured his heart and soul into The Twilight Zone and appropriately left more than a few mysteries behind when he passed away in 1975. In celebration of National Twilight Zone Day, here are five of the more fun and interesting tidbits.

5 Facts about The Twilight Zone

Serling Feuded with Ray Bradbury

While Serling was responsible for most Twilight Zone episode scripts, he also accepted submissions of story ideas in the hopes of giving quality writers their big break; he also reached out to already-successful and famous sci-fi writers to pen scripts. One who agreed to work on the show was Ray Bradbury of Fahrenheit 451 fame, who, despite his fame and having written several stories for the show, only saw one make it to people’s screens. Serling would later claim that Bradbury’s skills were best left to books and poor for TV while Bradbury countered by calling Serling a plagiarist. Serling remained a fan of Bradbury’s despite the horrible accusation, and it’s never been confirmed whether they eventually made peace.

It Launched Many Actors’ Careers

The Twilight Zone may have been a potential springboard for writers, but even more actors have used the series for exposure. Young actors who would go on to become very famous following being on the show include Burt Reynolds, Charles Bronson, Dennis Hopper, Robert Redford and more. The series is also notable for featuring three future members of the main cast of the original Star Trek: William Shatner (who appeared in more than one episode), Leonard Nimoy, and George Takei.

It’s a Constant Reference on The Simpsons

Speaking of, while people seem to better remember the connection between The Twilight Zone and Star Trek, the former actually has a strong connection with another long-running, popular show: The Simpsons. The show’s annual “Treehouse of Horror” Halloween episodes have parodied certain Twilight Zone episodes numerous times over the years, starting with the very first one; the most recent parody was in 2005. It’s happened often enough that a South Park episode later noted that something normally attributed to The Simpsons was actually referencing a Twilight Zone episode.

One Episode Was Supposed to Be a Spin-Off

The season three episode “Cavender Is Coming” was Rod Serling’s attempt at two things: comedy and creating a spin-off. The episode was about an angel who has one day to improve a woman’s life in order to finally earn his wings; the episode—which is also the only one to feature a laugh track—ends with him being assigned to help more people, potentially setting up a new series. The episode was poorly received and home video releases of the episode have the laugh track removed to this day.

Serling Hated Censorship

Rod Serling did not like corporate censorship, as it would result in what he saw as serious damage to many of his ideas. For example, racial commentary was removed from one episode and a plot-relevant building was removed from another because it was owned by a sponsor’s rival. The Twilight Zone gave him the creative freedom he needed to provide commentary on important topics such as religion and society without outside intervention, thus influencing many idea generators that followed.

BONUS: “There is a Fifth Dimension. . .”

Rod Serling himself served as narrator, speaking and later appearing at the start and end of every episode to present and close out each story. However, he wasn’t his own first choice; he originally wanted the famed actor and director Orson Welles to do it. Unfortunately, the amount of money Welles wanted to take on the task was beyond what Serling could afford, so Serling took up the reins himself.