Because Robert Zemeckis filmed the 2009 version of A Christmas Carol as a motion-captured 3D animated film, he had the ability to do things that could not be accomplished with traditional film.
One major example is the Ghost of Christmas Past, who takes Scrooge on a personal flight through his own past; Scrooge is physically removed from his flat and flown through the air. He is scared of the flight but then interested in the destination, and comes to realize that the ghost is necessary as he cannot fly by himself. 3D allows the audience to fly along with Scrooge and the Ghost as scenery and weather flies by.
Another example is the Ghost of Christmas Present, who shows Scrooge the joy of people in present times through a spectacular flyby sequence. The Ghost sprinkles sparks onto the floor, which becomes transparent and flies over and into houses, where people can be seen. Scrooge is initially terrified by the seeming hole, but soon becomes fascinated by the stories playing out below; the audience similarly is drawn in with the 3D effects as the scene seems to swoop and hover. This time, although the flying is similar, Scrooge is more rooted, exemplifying his later stability in life.