Goofs

The Chevy used by Cmdr Mathews in Hawaii had the same military number on the door as the one assigned to Cmdr Mathews in San Francisco.

When the helicopter carrying Carter lands, he gets into a police car, which drives off with the Golden Gate Bridge in full view in the background. This is right after the octopus has begun pulling itself up on the bridge's south tower, yet in the shot the octopus is plainly not on the bridge. Soon after, Carter drives that same police car out onto the bridge, but when he arrives in mid-span, the car is a different make, model and year, matching the (miniature) police car subsequently crushed by the octopus's tentacle.

In most shots of the octopus's tentacles wrapping around the clock tower, the clocks read 5:35, but in a couple of shots the hands show 9:25.

During the airplane search for survivors after the first monster attack, the pilot sights two men in a rubber raft in the ocean, but when the scene transitions to the naval hospital, four rescued sailors are brought in.

Closeups show the octopus on the Golden Gate Bridge. But when Carter lands in the helicopter and jumps into the police car, the bridge is clear.

Near the end of the film, when fear of the giant octopus is at its most frenzied, there is a highway scene purportedly showing people fleeing San Francisco in their cars. However, this shot actually shows traffic coming INTO the city. The shot is of I-80 west and the cars are just entering San Francisco from the San Francisco-Oakland Bay Bridge. It is evident that the traffic is flowing into San Francisco and not away from it, because one of the bridge's two towers can clearly be seen in the background perpendicular to the road. The "Bay Bridge" (as it appeared in 1955 and still appears today - a new bridge is currently under construction) consists of two spans connecting San Francisco and Oakland via a small island in the middle of San Francisco Bay. The western span connecting the island to San Francisco is a "double-deck" suspension bridge with traffic flowing into San Francisco on the top deck and traffic flowing out of the city on the bottom deck NOW, and for the last half century, but at the time of the movie, the upper deck had lanes of car traffic in both directions, whilst the lower deck had train tracks and bi-directional truck traffic. Cars were not "banned" from the lower deck, and traffic on the lower deck (both directions) was lighter than the upper deck. Eventually, in the 1960s, the train tracks were removed, and each deck was made one-way.

In the final scene, Commander Mathews' uniform does not have the star above the three stripes on his sleeve. This designation is worn by unrestricted line officers (those who command naval warships).

Cars shown were from the 1950s. One shot of a San Francisco street showed cars from the 1930s.

As the sub closes in on the octopus the captain tells the forward torpedo room to stand by, followed by stock footage of a torpedo room throwing switches: gauges move and the room shudders, a reaction that would indicate a torpedo had just been fired. When the command is given to fire the same crew is shown setting switches, but there's no comparable reaction as would be caused by a firing.

Early in the film, the submarine is a SST-1 Mackerel class training sub. Subsequent shots of the sub diving and underwater are WWII diesel submarines.

Faith Domergue says toward the end of the movie that another giant octopus attacked in the 12th Century as a result of the eruption of Mt. Vesuvius. The AD 79 eruption of Vesuvius is the most famous, but in the 12th century it erupted in both 1139 and 1150.

In the conference room whilst discussing what to do, a U.S. Marine comes in to deliver a message wearing his cover (hat). Normally, U.S. Marines do not wear their covers indoors; however, in this case, the Marine is wearing an MP patch, implying he was 'on watch', and so would be covered indoors.

In all the shots of the monster sprawled across the Embarcadero, cars can be seen driving normally along the street, even right under its tentacles. It is highly unlikely that motorists would continue to calmly drive past a giant octopus attempting to come ashore, let alone beneath its tentacles.

When the octopus's tentacles are waving behind and over one of the buildings near the Embarcadero, the tentacles cannot be seen through the building's open windows.

When the search plane is shown, it is a Martin PBM Mariner patrol bomber, but when the pilot is shown in a closeup, he is in a small, general aviation airplane - it appears to be a Beechcraft Bonanza.

When the octopus's tentacle is smashing the entrance to the ferry terminal, people are seen running away along the sidewalk on the right side of the screen. In a close-up of the fleeing people, the last stragglers, including several policemen, are shown running away. When the shot cuts back to the full scene, again showing the tentacle, there are suddenly many more people running along the sidewalk, and those stragglers appear once again at the very end of the scene.

After Carter leaves the submarine to fire a harpoon in the octopus's eye, the octopus can been seen through Carter's whole body.

Cmdr. Mathews is talking to Prof. Joyce in the research lab while smoking a cigarette even though there is a "No Smoking" sign on the wall behind them.

When a giant octopus attacks a ship and the order is given to abandon ship the crew are seen jumping overboard on the side that's being attacked. This was obviously for effect so the crew and octopus could be seen.

In his introduction for TCM, Ben Mankiewicz says the creature became a giant after absorbing radiation. But Dr, Joyce explains during the film that the creature was always a giant, and that radiation simply made it easier for the creature's normal food supply to escape it, forcing it to rise to the surface to seek other food sources. The hydrogen bomb forced it to the surface, but didn't cause its size.

In the 12th Naval District office the press are being briefed on the situation. When the map on the wall is shown in a close-up as he points to it the SF peninsula is missing because the lower half of the SF Bay is also missing. Surely the 12th Naval District would have a more accurate map.

The illustration shown to the press by Prof. Joyce depicts a supposed "kraken" attack on a French warship off the coast of Angola in 1810. The original illustration was by Pierre Denys de Montfort, who tried for decades to prove the existence of giant squids or octopi. He died about forty years before science accepted the reality of Architeuthis.

The opening sequence on the submarine, appears that Kenneth Tobey's character, the captain of the submarine is wearing the collar brass of a major, and his lieutenant is wearing the collar brass of a captain.

Correction: while on a ship, the ranking officer of a Naval vessel is referred to as "captain" even though he/she does not actually hold the rank of Captain (eagle insignia). Kenneth Tobey's character has the rank of Naval Commander (silver oak leaf insignia and three sleeve stripes on his dress uniform) and the other officer holds the rank of Naval Lieutenant (dual silver bars). The original goof refers to Army, Air Force, or Marine ranks. The Navy has different names than the other service branches for the same insignias.

There is no Harpers Cove Oregon.