This film marked one of the first times a science-fiction project had received a large budget. The genre had rarely been taken seriously by studio executives, and sci-fi films generally received the most meager of budgets. The critical success of this film convinced many in the film industry that well-funded science-fiction projects could be successful. Film historian Ben Mankiewicz has claimed that this film's success made future big-budget science-fiction films possible.
Star Trek (1966) creator Gene Roddenberry has been quoted as saying that this film was a major inspiration for that series. Perhaps not accidentally, Warren Stevens, who plays "Doc" here, would later be a guest star in 1968's Star Trek: By Any Other Name (1968), where the true shape of the alien Kelvans, like the Krell in this movie, was implied to be extremely non-humanoid but never shown. 1701, which is the serial number of the Starship Enterprise, allegedly comes from the clock mark 17:01 when the C57D enters orbit around Altair IV.
The model of the "flying saucer"-style Earth space cruiser was retained by the MGM prop department and subsequently used in a number of productions on the MGM lot, including The Twilight Zone: To Serve Man (1962). Robby the Robot, his ground transporter, and crew uniforms would be used on The Twilight Zone (1959) as well.
The opening narration states, "In the final decade of the 21st century, men and women in rocket ships landed on the moon." That would have been about 140 years after the film's 1956 date. The actual first moon landing occurred only 13 years after the film.
In addition to animating the monster that invades the camp, Walt Disney studios artist Joshua Meador provided approximately 29 other animation effects depicting laser beams and other forms of visual energy.
The film was originally conceived and approved by MGM's Dore Schary--no fan of science-fiction, as a "B" picture. The studio's art department, still headed by veteran Cedric Gibbons, pulled out all the stops. The budget ballooned to $1.9 million and its box-office returns barely managed to break even amid a dismal year for the studio. The relative failure of the film was cited as a reason for Schary's ouster soon after.
The scene in which the image of Altaira appears in the Krell's "plastic educator" device was achieved with several special effects, including superimposed film footage of the charge from an electrical generator, hand-drawn animation, and a traveling matte cut from film footage of Anne Francis.
The planet on which Edward and Altaira Morbius live is Altair IV, which according to Star Trek: Deep Space Nine (1993) is also a Federation planet. Director Fred M. Wilcox consulted with scientists before making the decision that the planet's sky would be green.
Louis Barron and Bebe Barron worked on the electronic soundtrack music "tonalities" for only three months, the length of time given them by Dore Schary, head of MGM. He authorized the studio to send them a complete workprint on Christmas 1955. They received the complete 35mm Eastmancolor workprint on New Year's 1956, a week later, still with many visual effects sequences missing and timed in with blank leader by editor Ferris Webster. From 1/1/1956 to 4/1/1956 they worked on the soundtrack score in their Greenwich Village studio in New York City while the film was in post-production in Culver City, CA. The score was completed and delivered to MGM on April 1, 1956, and the film was released for a studio sneak preview soon afterward. The musicians' union, however, objected to the soundtrack and blocked the Barrons from being credited as "composers", hence the term "electronic tonalities".
Robert Kinoshita, who is credited with building Robby the Robot, was also Art Director for the TV series Lost in Space (1965). Many of the "Lost in Space" robot's features are similar to Robby's: glass "head" with animated elements; rotating antenna "ears" (although the "Lost" robot's ears rarely moved after the pilot episode); flashing light "mouth"; chest panel with more animated elements. For that matter, much of the layout of "Forbidden Planet"'s spaceship is mirrored by "Lost"'s Jupiter 2: saucer shape; integral landing gear/entry stairs; lower external dome with animated lights; central, plexi-domed navigation station; vertical hibernacula arranged along perimeter. In addition, Robby and the "Lost" robot had a couple of "family reunions" in two "Lost in Space" episodes: Lost in Space: War of the Robots (1966) and Lost in Space: Condemned of Space (1967).
Studio chief Dore Schary and producer Nicholas Nayfack were unsure about releasing the film with a solely electronic score by Louis Barron and Bebe Barron. A rough cut of the film was previewed with the electronic score. The audience reaction to the film overall was so favorable that Schary ordered the rough cut to be released with the electronic score and no further editing.
MGM insisted on changes to Cyril Hume's script by adding comic relief scenes with the ship's cook (Earl Holliman). Among these scenes was one in which Robby the Robot responds to the cook's complaint about the lack of female companionship by bringing him a female chimp. The scene was reportedly not filmed.
To increase the sense of depth, the opening image of the spaceship approaching the camera is actually composed of two shots: the first of a small model, the second of a larger model travelling on the same track. The ship passes into and out of a shadow to conceal the cut.
Writers and special effects artists Irving Block and Allen Adler originally conceived of this film as a B picture and brought it to Allied Artists, which turned it down. They then decided to try their luck at MGM, then still Hollywood's most prestigious studio, which had not produced a science fiction film since The Mysterious Island (1929). To their surprise, studio chief Dore Schary green-lighted the project, immediately catapulting the film to the status of a major production.
The famous poster for the film shows a menacing robot carrying a struggling pretty girl - a staple of "monster movie" posters from the 1950's. In fact, no such scene occurs in the film itself and the robot portrayed in the poster is of course actually the very likeable Robby the Robot.
David Rose, composer of light orchestral music such as "Holiday For Strings", was originally hired to write the score. He was relieved of his contract by producer Dore Schary in December 1955 when Schary discovered avant-garde electronic music creators Louis Barron and Bebe Barron in a nightclub in Greenwich Village, New York, and hired them on the spot. The only confirmed piece of music which still remains from Rose's discarded original score is his Main Title Theme, which he released as a single on MGM Records in 1956.
The green sky paid homage to the 1933 novel "When Worlds Collide" by Philip Wylie and Edwin Balmer. In it, the sky on the primary alien planet was green. A species of green algae there used sunlight to separate water into hydrogen and oxygen and stored the hydrogen in sacs, allowing it to float in the air.
While plenty of previous science fiction films had earthlings exploring other worlds, Forbidden Planet was the first film to be set entirely on a foreign planet. While there are plenty of outdoor sequences in the film, all of them were shot indoors on a studio soundstage, while many exterior landscape shots are comprised of colorful and detailed matte paintings.
MGM had had a full animation department at one time but by 1956 it was largely dismantled. Critical animation effects (landing beam, weapons, Robby overloading, the Id Monster) were provided by Joshua Meador on loan to MGM from Walt Disney Pictures. Meador's recognizable style can be readily discerned from that of the other three effects animators working on Alice in Wonderland (1951) and in other Disney releases.
The line "You shall not look on the Gorgon's face and live" was originally said, or so the story goes, by the goddess Athene to Perseus, before she gave him a mirror-like shield (aegis) so that he need not look on her (Hermes gave him a sickle to kill the Gorgon). So Morbius is already showing a little of his fatal pride.
Early in the film, just after the spaceship drops out of light speed, the ship's speed is announced as .38 of light speed. That is still 254 million MPH. At that speed the ship could fly the path of a single Earth orbit in 137 minutes or travel from Los Angeles to New York in 4/100ths of a second.
Apart from the electronic tonalities composed by Louis Barron and Bebe Barron, the music score known to many as "Forbidden Planet Fanfare - Parts 1 & 2" on the original 1956 theatrical trailer was composed by André Previn, and pieced together seamlessly by an MGM music editor. The music was originally written by Previn for the MGM films Scene of the Crime (1949) and Bad Day at Black Rock (1955).
Robby the Robot's main designer and uncredited builder, Robert Kinoshita, distilled thousands of drawings conceived over five weeks by a team of five men into the final version. Prior to working in film, Kinoshita had designed washing machines, so while Robby had an anthropomorphic design in his upper regions, his chest and legs resembled a washing machine tub.
Irving Block and Allen Adler's original script took place in the year 1976 on the planet Mercury. An Earth expedition headed by John Grant is sent to the planet to retrieve Dr. Adams and his daughter Dorianne, who have been stranded there for twenty years. From then on, its plot is roughly the same as that of the completed film, though Grant is able to rescue both Adams and his daughter and escape the invisible monster stalking them.
The screenplay by Irving Block and Allen Adler, written in 1952, was originally titled Fatal Planet. The later screenplay draft by Cyril Hume renamed the film Forbidden Planet, because this was believed to have greater box-office appeal.
In late September 2015 several screen-used items from Forbidden Planet were offered in Profiles in History's Hollywood Auction 74, including Walter Pidgeon's "Morbius" costume, an illuminating blaster rifle, blaster pistol, a force field generator post, and an original Sascha Brastoff steel prehistoric fish sculpture seen outside Morbius' home; also offered were several lobby cards and publicity photos.
Cinematographer George J. Folsey wrote in an August 1955 American Cinematographer article about the film that the production had required two years of research. Among the more difficult and important props used in the film, he listed: the atomic cannon, the space Jeep, an electro-magnetic tractor and Robby, the robot. Several of the stages, including the Krel laboratory and the spaceship's interior, required extensive electrical wiring and control panels to make gadgets, meters and controls appear realistic. In addition, Folsey stated that light problems occurred repeatedly through the filming because of the number of reflective surfaces in the sets. Particularly, he suggested that the lighting effects to imply the body of the invisible "id monster" as it approaches the ship were the most difficult. Folsey stated that he shot the sequences from a height of ten feet, as if seen from the monster's eyes, and used shadowing and colour effects to produce the body's presence.
An August 20, 1954 Los Angeles Times article states that director Fred M. Wilcox had planned to do extensive research at several university libraries to use current scientific thought and experimentation to shape his portrait of the future.
Using ideas and procedures from the book Cybernetics: Or, Control and Communication in the Animal and the Machine (1948) by the mathematician and electrical engineer Norbert Wiener, Louis Barron constructed his own electronic circuits that he used to generate the score's "bleeps, blurps, whirs, whines, throbs, hums, and screeches". Most of these sounds were generated using an electronic circuit called a "ring modulator". After recording the basic sounds, the Barrons further manipulated the sounds by adding other effects, such as reverberation and delay, and reversing or changing the speeds of certain sounds.
The film was re-released to film theaters during 1972 as one of MGM's "Kiddie Matinee" features; it was missing about six minutes of film footage cut to ensure it received a "G" rating from the Motion Picture Association of America. Later video releases carry a "G" rating, though they are all the original theatrical version.
A full-size mock-up of roughly three/fourths of the starship was built to suggest its full width of 170 ft (51 m). The ship was surrounded by a huge, painted cyclorama featuring the desert landscape of Altair IV; this one set took up all of the available space in one of the Culver City sound stages.
MGM declined to publish a soundtrack album at the time that the film was released. However, film composer and conductor David Rose later published a 7" (18 cm) single of his original main title theme that he had recorded at the MGM Studios in Culver City during March 1956. His main title theme had been discarded when Rose, who had originally been hired to compose the musical score in 1955, was discharged from the project by Dore Schary sometime between Christmas 1955 and New Year's Day. The film's original theatrical trailer contains snippets of Rose's score, the tapes of which Rose reportedly later destroyed.
The Barrons finally released their soundtrack in 1976 as an LP album for the film's 20th anniversary; it was on their very own Planet Records label (later changed to Small Planet Records and distributed by GNP Crescendo Records). The LP was premiered at MidAmeriCon, the 34th World Science Fiction Convention, held in Kansas City, MO over the 1976 Labor Day weekend, as part of a 20th Anniversary celebration of the film held at that Worldcon; the Barrons were there promoting their album's first release, signing all the copies sold at the convention. They also introduced the first of three packed-house screenings that showed an MGM 35mm fine grain vault print in original CinemaScope and stereophonic sound. A decade later, in 1986, their soundtrack was released on a music CD for the film's 30th Anniversary, with a six-page colour booklet containing images from the film, plus liner notes from the composers, Bebe Barron and Louis Barron, and Bill Malone.
The trivia items below may give away important plot points.
According to various sources, when the crew members are firing at the Monster and it roars, menacingly moving its head from side to side (before it ultimately kills two of the crew members), the actions of the Monster are, in an "inside joke", actually mimicking those of "Leo the Lion", the MGM mascot who appears at the beginning of this and every other MGM film.
The special effects artists used split-screen traveling mattes to make images appear and disappear, such as the piece of fruit Morbius lobs at the "household disintegrator beam" and the tiger that Commander Adams vaporizes.