The ticket that gets lost often times floats almost exactly like the feather does in the beginning of "Forrest Gump" (1994), another Robert Zemeckis-Tom Hanks film.
The Polar Express is the very first feature film to be shot entirely in the new format of Performance Capture. The technique used in this film surpasses Motion Capture, in that Performance Capture has the ability to offer true human emotions and natural facial expressions with clear and precise detail. As many as 150 reflective jewels were adhered onto the actors' faces, including eyelids, brows, upper and lower lips, chin line and cheeks, which took nearly two hours to achieve. With this technique, Tom Hanks is able to portray five key characters in this film, which was in production for over two and a half years.
While Smokey and Steamer are floating in the engine cabin while trying to capture the cotter pin, the Flux Capacitor from Back to the Future can be seen flickering to the left. This was deliberately added as an in-joke, because both were directed by Robert Zemeckis.
After Hero Boy pulls the whistle in the locomotive cab, he says, "I've wanted to do that all my life". This exact same line was said by Doc Brown (Christopher Lloyd) in Back to the Future Part III, after he pulls the whistle in a similar type of steam locomotive. Both these films were directed by Robert Zemeckis.