Goofs for
Forbidden Planet (1956) More at IMDbPro »

• Crew or equipment visible: As the vehicle driven by the robot first drives up to the residence, there is a tow cable visible in the foreground, partially obscured by the bushes. This cable is most visible behind the vehicle as it leaves the scene.
  
  
• Revealing mistakes: As the tiger passes Altaira on the patio, first a portion of the tiger's face, and then a portion of the tiger's hind leg vanish in the split-screen effect.
  
  
• Continuity: Dr. Morbius invites Commander Adams to try his blaster on the Krell metal door. Cmdr. Adams inspects the result, but he's not pointing to the spot where the beam hit.
  
  

• Continuity: During the kissing lesson, Jerry goes from embracing Altaira to holding her by the arms between shots.
  
  
• Revealing mistakes: During the landing scene, the shadow of the ship (or a supporting structure of the suspended model) is visible briefly moving across one of the smaller mountains at the right side of the screen.
  
  
• Revealing mistakes: When Robby uses the blaster on the plant in the garden, an unidentifiable shadow suddenly appears on the green V support directly behind Commander Adams.
  
  
• Crew or equipment visible: When the ship's cook is picked up by the magnetic crane, one of the wires that really picks him up is clearly visible.
  
  
• Revealing mistakes: In several wide shots of the crew members outside the ship, there is a faint vertical shadow visible on the painted backdrop behind the ship. It appears to be either a fold in a piece of fabric or the corner of the sound stage wall.
  
  
• Continuity: When the id-monster is burning its way through Krell metal to get into the lab, Commander Adams is seen reaching for his blaster (apparently to kill Morbius) while it was already rendered useless by Robby when Adams tried to force his way into the house a few scenes earlier.
  
  
• Factual errors: The star Altair is shown as an orange-red star, eclipsed by one of its (spherical) planets. It is now known that Altair is white and is oblate, with its equatorial diameter 14% greater than its polar diameter, something that was not known when the movie was produced.
  
  
• Revealing mistakes: As Altaira emerges from the swimming pool, the flesh-coloured suit that she is wearing to give the impression of nudity is visible.
  
  
• Factual errors: The robot shows up carrying lead shielding, which he says is "isotope 217", and he implies it is lighter than ordinary lead. The purported isotope lead-217 does not exist, and if it did, it would be 4% heavier than the most common (and heaviest) isotope of lead (number 208), not lighter.
  
  
• Continuity: The sudden appearance of the cook behind the officers after Robby first arrives at the ship and his subsequent position relative to them before they leave with Robby.
  
  
• Revealing mistakes: In the scene where the monster approaches the house from the southwest and Morbius commands Robby to destroy it, with Robby short circuiting due to logic conflict between obeying Morbius and knowing that destroying the monster (id of Morbius) would destroy his master, just before the shot ends after Robby is supposedly immobile, his arms wiggle.
  
  
• Continuity: When Dr. Morbius is showing Doc and the Commander around the Krell labs, his outfit is originally black. Later, it turns brown and stays that way - although the cut of the outfit is still identical.
  
  
• Continuity: The steps were crushed when the Id entered the spaceship, but in a later scene you can see none of them are damaged.
  
  
• Crew or equipment visible: When the Monster is burning / melting the metal door, as it turns white hot and lumps start to fall, you can see a member of the crew, in a heatproof suit (watch the second and third holes for movement behind the door), as well as the 'tool' they use to push the burning metal to the floor.
  
  
• Continuity: As Alta talks to the commander after being found kissing Lt Farman, her position changes from being side-on to face-on to the commander.
  
  
• Revealing mistakes: As Morbius shows the Commander and Doctor around the Krell underground complex, sometimes they cast shadows on the ground and sometimes they do not. Also at one point their reflections can be seen in puddles of (rain)water lying on the surface on which they are walking.
  
  
• Plot holes: Robby informs the crew that if they do not speak English, he is at their disposal with "187 languages"; yet, he says it all in English. If the crew did not speak English, how could they know what he was saying?
  
  
• Plot holes: When Dr. Morbius is showing the commander around the alien installation for the first time he uses combination lock to open the lab door. How did he know the combination if the aliens died so long ago?
  
  
• Revealing mistakes: When the electronic protection fence is activated around the perimeter, the beams have to be turned off for the cook or anyone else to go through the posts. But, when the commander orders two men to take flanking positions outside the fence, both men run right through it.
  
  
• Miscellaneous: When the C57D starcruiser is landing on the planet, it slowly eases down to the surface in a gentle "descending/ascending" manner. In one of the descents, it slams into the surface, then rises up and settles more gently. This quite likely would have broken some instruments on board the ship.
  
  

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