The scene where the Giant's hand was in the living room, watching a Maypo cereal commercial, was changed in the "Signature Edition" to an ad for the Disneyland attraction, Tomorrowland. Brad Bird had originally wanted the Tomorrowland ad in the movie, as an homage to his mentors, but Disney would not give him clearance to use it. Coincidentally, Bird ended up directing the movie Tomorrowland (2015).
"Frank" and "Ollie," the two trainmen that Kent interviews after the derailment, are caricatures of Disney classic animators Frank Thomas and Ollie Johnston. They also perform the voices for the characters. Animation writer Earl Kress has said that "Frank and Ollie are also life-long train enthusiasts and have extensive scale model railroads in their backyards like Walt Disney used to have."
In order to better blend the computer-generated Giant into the traditionally animated film, technicians came up with a program that gave the Giant's lines a slight "wobble," in order to match the natural line imperfections found in hand-drawn animation.
Although the movie received high praise from critics, it was deemed a box office failure, grossing only 23 million dollars after a reported seventy million dollar budget. The low earnings were partly due to the fact that the film debuted the same weekend as the successful The Sixth Sense (1999) (August 6, 1999).
The "3" on the A-113 license plate on the car partially eaten by the Giant is bitten off. Also, in Dean's house there is a painting which has "A113" on it. (A113 (sometimes A-113 or A1-13) is an inside joke, an Easter egg in animated films created by alumni of California Institute of the Arts, referring to the classroom used by graphic design and character animation students)
Production Designer Mark Whiting (a Michigan native) placed a Detroit Lions pennant in Hogarth's room, convincing Brad Bird that it was logical for someone in Maine (which doesn't have a team) because the Lions were the best team in the 1950s.
Was originally meant to be a musical. Pete Townshend and Des McAnuff developed it as a stage musical, using songs from Pete Townshend's concept album "The Iron Man" (much like the stage version of The Who's Tommy (1975)). Des McAnuff decided it would work better as an animated feature and pitched it to Warner Bros.
When the Giant's hand is "watching" television, the clip that was to be playing would have been the opening to Walt Disney's Wonderful World of Color (1954), but the filmmakers could not secure the rights, and substituted the Maypo commercial instead.
Dean's newspaper in the diner scene had an ad for RINSO, THE GRANULATED SOAP clothing detergent, which was a very accurate ad (and image) of the time, down to the silhouettes of "happy home-makers" on the box.
Among the comics Hogarth shows the Giant, is an issue of "The Spirit." Since the comic-book version ended in 1950 ("The Spirit" was a newspaper comic originally), it is unlikely (although not impossible) that Hogarth would have had any issues by 1957. In the 1990s, Brad Bird attempted to get backing for a "Spirit" animated film.
The newspaper headline that Dean McCoppin is reading ("Disaster Seen as Catastrophe Looms") is similar to the headline that Jim Dear is reading in Lady and the Tramp (1955) and that Jiminy Cricket is reading in Fun & Fancy Free (1947).
The town of Rockwell, Maine has a name suspiciously similar to Roswell, New Mexico, where aliens allegedly crash landed in 1947. It may also be an allusion to painter Norman Rockwell, famous for his idealized scenes of American small town life.
When Kent is using the Hughes' phone, the humorous oven mitt hanging on the wall beside him appears to be a stylized version of the "family dog" from director Brad Bird's animated short of the same title, Amazing Stories: Family Dog (1987).
Cloris Leachman's character, Mrs. Tensedge, originally appeared in another scene of the movie as well as more dialogue, according to a deleted pencil test scene. The scene ended up being removed from the story due to time restraint. In the film, she only says seven words.
The fighter planes used in the film are FJ-2/-3 Furies, the Navy version of the F-86 Sabre, adapted for carrier based operations in 1951. They were the first jets to be launched by steam catapult, as depicted in the film.
When Hogarth goes to check the antenna on the roof after the television stops working, it has been bitten off. This is a deliberate reference to the "Metal-Munching Mice" in a Rocky and Bullwinkle story.
The trivia items below may give away important plot points.
One of the scenes not included in the original theatrical cut of the movie involves a dream sequence depicting images of the Iron Giant's race, and their conflict that drove him from his home-world leading to his crash-landing on Earth. The scene is added to the movie in the Signature Edition.
The Iron Giant roughly takes place on a five-day period (Wednesday through Sunday). On Wednesday night, the Giant crash lands on Earth. After school the next day, Hogarth visits his mom at the diner and that night he encounters the Giant. It is now Friday and Hogarth goes to school and afterwards goes and finds the Giant. That night, he meets Kent and then Hogarth and the Giant find themselves at Dean's junk yard where the Giant has food and a place to rest. Saturday is when Kent questions Hogarth all morning. Hogarth visits Dean and the Giant that afternoon and go to the lake and witness the death of the deer. At night, Kent interrogates Hogarth and informs the army of the Giant's existence. The army arrives in the morning and fights the Giant and then the Giant saves everyone.
Also spoiler for Guardians of the Galaxy (2014): The Giant and Groot in Guardians of the Galaxy are both voiced by Vin Diesel and, in both times, the sound technician that worked on it was Doc Kane. Both characters end up sacrificing themselves, but are ultimately resurrected.
In the big battle scene, there is a moment when the Iron Giant fires at a tank, and before the energy ball hits, that two tank crewmen jump out before the tank disappears. This harkens back to the famous scene in The Day the Earth Stood Still (1951) when Gort fires at a tank on the Washington Mall and the two crew jump out before Gort's weapon dissolves it.