Much as the Lord of the Rings character Gollum was digitally mapped and reproduced via CGI, so too is Tom Hanks computer-generated here as a bald train conductor who looks like Tom Hanks. But he has also been digitally mapped to create a performance for Santa Claus. And a 10-year-old boy. Yet the boy is voiced by Daryl Sabara, and some of his movements are based not on Hanks, but on Josh Hutcherson. It's a lot to take in, but it mostly works. Chris Van Allsburg's book about a train ride to see Santa Claus is used as a source for the beginning and for the final 20 minutes. In between, director Robert Zemeckis has created an action movie for kids, in which our main characters find themselves either hanging off the side of the train or trying to stop it from running too fast in the wrong direction. The climax is a bit sappy, but if you're lucky enough to see the film in 3-D IMAX, those objections are easily ignored.