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.
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 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 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.