A close examination of all the ticket numbers reveals that they all contain the number "1225" in them. 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 film used 3D motion capture techniques to digitally record the physical performances of the actors before "skinning" them with their animated forms. All the children's roles were acted by adults using oversized props to get the movement right.
The train set seen at the end is a recreation of the new Lionel Polar Express train set combined with the older Lionel Berkshire and the older tubular track.
In the beginning of the movie, Hero Boy looks at a picture of himself on a store Santa's lap. The store's name on the photo is Herpolsheimer's, an old department store in Grand Rapids, Chris Van Allsburg's hometown. Later the train passes by the store.
The address spoken by the conductor early in the film "11344 Edbrooke" is the real address of Robert Zemeckis' childhood home. The home is in a south side of Chicago neighborhood called Roseland.
The locomotive in the movie is based on the Pere Marquette 1225, a restored steam locomotive located in Owosso, MI. In fact, many of the sound effects of the film's train are recordings of the actual train. The train is often run between Owosso and nearby Chesaning for rides during festivals.
The Hero Boy has a University of Michigan pennant (featuring the well-known maize-colored "block M") on the wall behind his bed. Chris Van Allsburg is a real-life graduate of the University.
The lonely boy is played by Peter Scolari, who starred alongside Tom Hanks (the Conductor) in Bosom Buddies. It was the first significant role for both actors.
Before the hero boy boards the Polar Express, the clock shows that it is 11:55. The time does not change until the first gift of Christmas is given near the end of the film.
The trivia items below may give away important plot points.
The visuals for North Pole City are based on the architecture of the Pullman plant (the company that made railroad cars) in Chicago, IL, near the childhood home of Robert Zemeckis in the Roseland neighborhood. The clock tower that Santa comes out of is based on the Pullman factory clock tower and many of the other buildings are based on Pullman's unique architecture.
The scene in the North Pole City communications room features 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.
Santa's reflection can be seen in the sleigh bell for just a few seconds, when it is shown in close-up, after Hero Boy places the bell on the table, at the film's end.