The film used 3D motion capture techniques to digitally record the actors' physical performances before "skinning" them with their animated forms. The children's roles were acted by adults, using oversized props to get the movement right.
When the Hero Boy first meets the Hobo on the roof of the train, he is playing the carol "Good King Wenceslas." The story of Saint Wenceslas I, Duke of Bohemia is that of a king braving the harsh winter to bring alms to the poor on the Feast of Stephan, December 26th. His page finds he can't go on through the harsh conditions and is directed to walk in the footprints that the king has made in the snow. The Hobo directs Hero Boy to follow behind him and ultimately helps him reach the engine before they make it to the tunnel, thus allowing him to find and help his friend. This is also a representation of the Holy Spirit idea of the Hobo, that he guides those who believe in Him to safety, even in perilous times.
Hero Boy's real name is never mentioned. However, according to books containing information about The Polar Express, including art books and fact books, Hero Boy's name is Chris, after the novel's author, Chris Van Allsburg.
The soldier doll that Hero Boy plays with on Christmas morning is part of the recycled toy program the conductor mentions. The same toy appears as a puppet in the background of the scene with the Scrooge puppet.
A close examination of the ticket numbers reveals that they all contain the number 1225. Pere Marquette No. 1225 was used as a model for the Polar Express locomotive. 12-25 also refers to the date of Christmas, December 25th.
The locomotive in the movie is based on the Pere Marquette 1225, a restored steam locomotive located in Owosso, MI. Many of the film's train sound effects are recordings of the actual train. The train runs between Owosso and nearby Ashley during the holiday season.
In the beginning of the movie, Hero Boy looks at a picture of himself on a store Santa's lap. The store is Herpolsheimer's, an old department store in Grand Rapids,Michigan, Chris Van Allsburg's hometown. Later, the train passes by the store.
A University of Michigan pennant is on the wall behind Hero Boy's bed. Chris Van Allsburg is a real-life graduate of the University. Pere Marquette 1225, the locomotive used as the basis for the one in the film, was donated to the Michigan State University after being retired from active service. It was displayed on the campus from 1957 to 1983.
Several reviews called the motion-capture animation "creepy." In the 1978 book "Robots: Fact, Fiction, and Prediction", Masahiro Mori coined the term "uncanny valley" to describe the revulsion that people can feel when they encounter a robot that looks human enough, but is clearly not alive.
The trivia items below may give away important plot points.
In the North Pole City communications room, an elf describing a bad little boy in New Jersey named Steven who is terrorizing his two little sisters. This line is a nod to Robert Zemeckis' friend and mentor, Steven Spielberg. Spielberg grew up in New Jersey, and has admitted many times that he frequently terrorized his two younger sisters.
The opening scenes, particularly in Hero Boy's bedroom, include two closeups of a chrome hubcap with a baseball lying next to it. During the second closeup of the hubcap as the boy's parents leave his room for the night after checking in on him, a small reflection of the Polar Express train is visible in the center of the hubcap.
The visuals for North Pole City are based on the architecture of the Pullman plant, maker of Pullman railroad cars, in Chicago. The clock tower, which Santa comes out of, is based on the Pullman factory clock tower. Many of the other buildings are based on Pullman's unique architecture.
The Polar Express is another Christmas Carol movie. Hero Boy is Scrooge and doesn't believe in Santa anymore causing the three ghosts of Christmas (the Hobo, Conductor, and Santa) to change him forever. The Hobo is the Ghost of Christmas Past, and plays the role of Christmas Future. He tries to intimidate Hero Boy into changing his ways using only himself instead of the future. The Conductor is the Ghost Christmas Present and is in charge of keeping order in the present to get Hero Boy to Santa. Finally, Santa is Christmas Future and changes Hero Boy forever, like Scrooge was. They even pay homage to Dickens' classic by having a Scrooge puppet dance on screen briefly. (Controlled by Christmas Past)
At the end when Hero Girl gets her ticket punched, the ticket reads Lead. Hero Girl thinks it reads "lead," like "lead balloon," but is told by the conductor, I believe it is pronounced "lead". As in "leader," "leadership." "Lead the way." Follow you anywhere ma'am. This is the same reference to how Led Zeppelin got their name, when Keith Moon said the band would go over like a "lead balloon." Jimmy Page remembered this years later when naming the band, knowing they would get mistaken for the word "lead," he named it "Led Zeppelin."