M*A*S*H had an episode centered around Boxing Day (the holiday for December 26). It's the only one I'm aware of, are there any other shows that had Boxing Day episodes?

On The Buses had a Boxing day episode.

From IMDB:
Season 5, Episode 15
Boxing Day Social (26 Dec. 1971)



It's Boxing Day and Arthur's mother has come to stay, along with his sister Linda,who throws herself at all the men, including Jack. The two families go to the bus company's dance where Arthur warns Jack to keep away from Linda but is himself the object of desire for conductress Beryl, leading to Olive causing a scene. Later, as Blakey shows Arthur's mother around the depot, they catch Stan and Linda in a compromising position.
- Written by don @ minifie-1

That's cool that MASH had a Boxing Day episode! I know it's not a holiday in the US but I wish more shows would talk about it, b/c it's such an interesting holiday!