Goofs

The same license plate (345ZZ) is used for two separate cars in the movie.

The stock of Hogarth's gun changes in appearance. When Marv Loach hands it to Kent Mansley, the "HOG" of "HOGARTH" is almost directly over the "HUG" of "HUGHES". When Kent looks at the gun in the car, the "HUG" has shifted the equivalent of two letters to the right.

When Hogarth first meets Dean in the Diner, the newspaper ad is "Moon Explorer". When Hogarth pulls the paper down the ad has changed to "First Lady".

As Hogarth runs from the Giant, he hits his head on a branch and falls. In the next shot, Hogarth is lying on a clearing, with no sign of the branch.

A scene midway through the movie reveals a sign on the side of Dean's tow truck that reads "McCoppin Scrap". The end credits offer us an alternate spelling: Dean McCoppen.

There are a few misspelled items that are unlikely to be in-universe errors: a shop Hogarth rides by at the start is spelled "BOUTIQE"; Dean's newspaper talks about a "SATELITE".

The fighter planes depicted in the movie, F-86 Sabres, did not carry missile pods as shown, nor were they equipped with afterburners, as shown during the 'scramble' takeoff sequence.

When Hogarth leaves the house to encounter the giant for the first time, a crescent moon is shown touching the horizon. The TV station has not signed off, and the plot suggests it is a time when kids are in bed but adults are still up, so it has to be before midnight. However, the moon's crescent is to the left, which would indicate a waning moon rising in the east shortly before sunrise.

A US Army jeep pulls in and attacks the Iron Giant with a mounted M1919A4 .30 caliber machine gun. However, the one in the film is equipped with spade grips, while the actual M1919A4 would have had a single pistol grip.

The sub, supposedly the Nautilus, has missile firing hatches and the body of a Soviet era submarine. US Navy subs, other than the Regulus missile carriers, weren't so clunky looking.

When the deer comes to the giant, the giant's finger appears proportionally bigger. The deer appears very small compared to the tip of the giant's index finger, considering the giant's whole hand was able to fit in the bathroom.

When the Giant is being electrocuted, he causes the power to go out in Rockwell. Annie is in the house, and in the shadow appears to grab a flashlight from the table. However, in the split second before the lights went out, the flashlight was not on the table.

Mansley says that the unidentified object entering Earth's atmosphere was assumed by some to be "a large meteor or downed satellite." In 1957 Sputnik was the only man-made satellite in orbit, so the idea of a "downed satellite" is premature.

Dean is called a "Beatnik" during the film which is set in 1957. The term "Beatnik" was coined by Herb Caen of the San Francisco Chronicle on April 2, 1958 as a derogatory term, a reference to the Russian satellite Sputnik, which managed to suggest that the beats were (1) "way out there" and (2) pro-Communist.

Set in 1957, in one scene The Iron Giant is seen playing with a 1959 Cadillac.

Guided air-to-air missiles were not in service in 1957.

The nuclear-powered submarine USS Nautilus (SSN-571) is depicted as a fleet ballistic missile (FBM) submarine. However, the Nautilus was a torpedo-carrying attack submarine. Also, the Polaris FBM program was not operational until autumn 1960. Furthermore, the missile being fired is reminiscent of a UGM-73 Poseidon C3 missile, not fielded until 1972 on the Lafayette and James Madison-class SSBNs.

At the beginning of the film, Sputnik is shown orbiting from East to West. All non-polar orbits of satellites run West to East, in order to take advantage of the Earth's rotation.

The train that collides with the Giant's head is pulled by a Norfolk and Western Railroad locomotive. The N&W never operated in Maine. Also, the locomotive is a streamlined passenger type, which wouldn't be pulling a freight train.

When Kent Mansley meets Marv at the power station, he tells Marv his name is Kent Mansley. But after Kent's car gets stolen by the Giant, Marv asks "What are we looking at Mr. Manly?" Instead of Mansley.