A Christmas episode told in the style of a Halloween episode, in three parts.

The first story sees Bart riding The Polar Express to the North Pole to confront Santa over a long-wanted dirtbike.
The middle story has the Simpsons children missing their mother Marge as she is away in Europe fighting for her country in WWII.
The last segment is quite unique and features the Simpsons as muppets with a live guest appearance from singer Katy Perry.

*Read a more detailed summary for this episode on Wiki Simpsons