The name "Robbie" (spelled with an "ie") had appeared in science fiction before Forbidden Planet. In a pulp magazine adventure The Fantastic Island (1935), the name is used for a mechanical likeness of Doc Savage used to confuse foes. The name is also used in Isaac Asimov's short story "Robbie" (1940) about a first-generation robot designed to care for children. In Tom Swift on The Phantom Satellite (1956), it is also the name given to a small four-foot robot designed by Tom Swift Jr., the boy inventor in the Tom Swift Jr. science fiction novel series by Victor Appleton II.
Robby the Robot originated as a character in the 1956 MGM science fiction film Forbidden Planet. The story centers on a crew of space explorers from Earth who land their starship, the C57-D, on the planet Altair IV, ruled by the mysterious Dr. Morbius. Robby is a mechanical servant that Morbius has designed, built, and programmed using knowledge gleaned from his study of the Krell, a long-extinct race of highly intelligent beings that once populated Altair IV. The film’s plot appears loosely based on William Shakespeare’s play The Tempest (1610), with the planet Altair IV standing in for Shakespeare’s remote island and Dr. Morbius for Prospero. In this context Robby is analogous to Ariel, a spirit enslaved by Prospero.
Robby exhibits artificial intelligence, but has a distinct personality that at times exhibits a dry wit. He is instructed by Morbius to be helpful to the Earthmen and does so by synthesizing and transporting to their landing site 10 tons of "isotope 217", a lightweight though still effective replacement for the requested lead shielding needed to house the C-57-D’s main stardrive to power an attempt to contact Earth base for further instructions. Morbius programmed Robby to obey a system of rules similar to Isaac Asimov’s Three Laws of Robotics as expressed in I, Robot (1950). One of the laws is a rule against harming or killing humans; this becomes an important plot point near the conclusion of the film when Robby refuses to kill the Id monster. The robot recognizes that the invisible creature is an alter ego/extension of Dr. Morbius. Hollywood purposely, and misleadingly, depicts Robby in the film’s advertising posters as a terrifying adversarial creature carrying a seductively posed unconscious maiden, but no such scene is in the film and the images do not reflect in any way Robby's benevolent and intelligent character. Robby only carries one person during the film, the Earth starship's Dr. Ostrow, when he is mortally wounded near the end of the film.
Robby was designed by members of the MGM art department and constructed by the studio's prop department; The design was developed from initial ideas and sketches by production designer Arnold "Buddy" Gillespie, art director Arthur Lonergan, and writer Irving Block. These concepts were refined by production illustrator Mentor Huebner and perfected by MGM staff production draughtsman and mechanical designer Robert Kinoshita.
The robot's groundbreaking design and dazzling finish represented a radical advance on the conventional "walking oil-can" depictions of robots in earlier features and film serials, and the only previous film robot of comparable style and quality was the "Menschmaschine" created for Fritz Lang's Metropolis (1927). However, this did not come cheap: As with every aspect of the production of Forbidden Planet, MGM spared no expense on Robby's design and construction. At a reported cost of US$125,000 (equivalent to at least $US1.1 million today) it was, proportional to total budget, one of the most expensive single film props ever created up to that time, which represented nearly 7% of the film's total budget of US$1.9 million. (By way of comparison, Robby cost roughly the same, proportional to total budget, as the massive 27-ton, 12 meter-diameter, rotating centrifuge set built for Kubrick's 2001: A Space Odyssey, which cost US$750,000 against a total budget of around US$11 million). But thanks to its imaginative design, intricate detailing, and the very high visual quality of the final product, Robby immediately became the "face" of the film and soon became an enduring popular culture icon.
The Robby suit was constructed using a range of materials including metal, plastic, rubber, glass, and Plexiglas. The plastic parts were a pioneering example of the use of the then novel technology of vacuum-forming heated plastic over wooden molds. These parts were made from an early form of ABS plastic with the brand name "Royalite", a material mainly used at the time for making suitcases. The finished suit stands just over 7-foot (2.1 m) tall and was fabricated in three detachable sections: the legs and lower torso, the barrel-like chest section (which included the arms), and the highly detailed 'head'.
The tall conical plexiglass dome that covered the head housed the detailed mechanisms representing Robby's electronic brain. These included a "pilot light" at the very top, an intricate apparatus terminating in three white wire-frame spheres that rotate in planetary fashion (representing his gyroscopic stabilizers), a pair of reciprocating arms in the shape of an inverted "V", multiple flashing lights, and an elaborate horizontal array of moving levers resembling saxophone keys. Conical protuberances attached to each side of the head carry two small forward-facing blinking lights (his eyes) and two rotating chromed rings, one mounted vertically and the other horizontally, which represent Robby's audio detectors (his ears). The bottom front section of the head is a curved grille consisting of parallel rows of thin blue neon tubes, which light up in synchronization with Robby's voice. This neon grille also enabled the operator to both see out and to breathe. The joint between the head and chest section was fitted with a custom-made bearing that allowed the head to rotate 45 degrees in either direction.