Using similar technology that was used on Polar Express and Beowulf (where the tech was much improved), Disney’s A Christmas Carol uses a mixture of CG animation and "performance capture." Think motion capture, but swap out the first word with "performance" and you pretty much have the same thing.
In the featurette we get to see director Robert Zemeckis and Jim Carrey discuss the technology while showing some temp footage from the film. The coolest part, however, was all the different ages of Scrooge. Check it out below (via TrailerAddict):
Disney's A Christmas Carol opens to theaters on November 6th.