The Dark Crystal was a Jim Henson production that received a lukewarm reaction from viewers and critics alike when it was released in 1982—in large part because Henson fans, who were used to seeing lovable Muppets, instead witnessed something truly unique. Now a cult classic, the live-action fantasy adventure centers around Jen and Kira, the last two members of the Gelfling tribe, who are trying to stop the evil Skeksis from conquering the world. Here are some facts about the film that was advertised as the first movie to not have a single human actor.

1. ILLUSTRATOR BRIAN FROUD WAS DISCOVERED BY JIM HENSON SIX YEARS BEFORE THE DARK CRYSTAL WAS RELEASED.

Henson saw some art from the British illustrator in a book called Once Upon a Time, and soon asked him to collaborate. The movie was a combination of imagery from the minds of both Henson and Froud. Henson credited Froud with developing The Dark Crystal’s “symbolic structure.”

2. FROUD GOT HIS DESIGN IDEAS FROM EATING LOBSTER DINNERS.

After enjoying his meals he would glue the shells together for design inspiration.

3. BRIAN FROUD MET HIS WIFE ON THE SET.

Brian Froud met his future wife, puppet designer Wendy Midener, while in production on The Dark Crystal when she was hired to sculpt 3-D versions of Brian’s Gelfling designs for the movie. She later sculpted and helped puppeteer Yoda for The Empire Strikes Back.

4. HENSON WROTE THE MOVIE'S ORIGINAL OUTLINE WHILE SNOWED IN AT A HOTEL.

On February 6, 1978, Henson and his daughter Cheryl were forced to spend the night at a Howard Johnson’s at John F. Kennedy Airport in New York City in the midst of a blizzard. With little else to do, Henson hand-wrote multiple pages of the movie’s outline for screenwriter David Odell to work with.

5. HENSON MADE A MANDATORY BOOK RECOMMENDATION.

Both Brian Froud and The Dark Crystal screenwriter David Odell were told by Henson to read Jane Roberts’s 1972 book Seth Speaks: The Eternal Validity of the Soul, based on Roberts’s experiences channeling a multi-dimensional being that existed outside of time and space. Odell claimed Aughra’s line “He could be anywhere then” was influenced by Roberts’s book.

6. THE ORIGINAL GRIMM’S FAIRY TALES WERE ALSO AN INFLUENCE.

Frank Oz recalled that Henson wasn’t afraid to possibly scare the children who were his fans from the Muppet movies and his puppets from Sesame Street. He wanted to “get back to the darkness” of the original stories by the Brothers Grimm.

7. IT WAS FRANK OZ’S FIRST DIRECTING JOB.

In addition to the famous puppeteer performing as Aughra and Chamberlain in the film, Oz accepted Henson’s request to co-direct the film. Oz estimated that Henson helmed “70 percent” of the movie. Having two directors was so confusing and slowed things down for the crew so much that an assistant director was tasked with informing Henson and Oz that everybody wanted Henson to direct himself. He denied the request.

8. SIX PERFORMERS WERE OPERATING EACH CREATURE SIMULTANEOUSLY.

It took six people to work the animatronic Skeksis creatures: two were stuffed in the bird-like body while four worked on a platform underneath the surface. One group of performers worked for at least six months before shooting even began.

9. THEY SHOT THE MOST COMPLICATED SCENES FIRST.

Shooting began on April 15, 1981. One of the first scenes shot was the big showdown between Jen and Kira and the Skeksis in the Crystal Chamber.

10. HENSON MODELED THE SKEKSIS ON THE SEVEN DEADLY SINS.

That would be wrath, greed, sloth, pride, lust, envy, and gluttony. (Since there were more than seven of them, some of the sins were repeated.) Froud described them as parts reptile, predatory bird, and dragon.

11. IT WAS ALL SHOT WITH A FAINT COLOR TINT TO RESEMBLE FROUD’S CONCEPTUAL DESIGNS.

This was done with a “light flex” by Oscar-winning cinematographer Oswald Morris, who retired after his work on The Dark Crystal.

12. THE SKEKSIS AND MYSTICS ORIGINALLY HAD AN INDO-EUROPEAN ROOTED LANGUAGE.

David Odell wrote in the original script for the Skeksis and the Mystics to share a similar language, with the Skeksis using a “cruder, uglier” version of it. However, the actors were too busy trying to work on their movements to learn new words, so they mostly spoke gibberish. Until ...

13. THE FIRST PREVIEW AUDIENCE HATED THE MOVIE.

On March 19, 1982, a Washington D.C. crowd was one of the first groups of people to ever witness the original cut—and they didn't like it. Mostly because they were confused and unhappy with not understanding what the Skeksis were saying. Henson asked Odell to add some voiceovers as well as some new dialogue so that the Skeksis could be re-recorded into English.

14. HENSON PAID $15 MILLION OF HIS OWN MONEY TO BUY THE FILM FROM ITS STUDIO.

ITC Entertainment had new leadership in the form of Robert Holmes à Court, who gave the film little advertising after its bad first screening. Worried his baby wasn’t going to get the chance it deserved, Henson spent all of the money he had available to buy his movie from Court. The movie came in third on its opening weekend (losing to Tootsie and The Toy), but the movie that was made on a $15 million budget eventually ended up making $40 million at the box office.

15. A SEQUEL HAS BEEN IN THE WORKS FOR A WHILE.

It has been reported that Jim Henson’s children and some of the original creative term have been working on Power of the Dark Crystal, a sequel, for many years now. Director Shane Abbess left the project because executives wouldn't allow him to follow through on Henson’s handwritten notes on what he wanted the sequel to be.