Downton Abbey a Rare Popular Hit on PBS

It's not often that a show or program that appears on America's PBS has mass appeal, much less any following whatsoever with young adults. But the British-produced World War I-era drama "Downton Abbey," has achieved just that. Brought to American audiences via the public station, the show and its cast of lords, ladies, cooks and maids has caught the fancy of the American public in a manner that simply could not have conceivably been predicted.

The open of the second season was in January on PBS's "Masterpiece" and attracted 4.2 million U.S. viewers. That's an 18% increase over the first season. It's also more than the regular audience for "Mad Men" and close to "Kourtney and Kim Take New York." And while British royalty always seems to have a special draw for Americans, the really interesting aspect of the show is the popularity it is enjoying on social media websites, where much of its promotion is occurring virally.

Now, PBS has something more to look forward to, as Shirley MacLaine will join the cast and will play the mother of the American heiress Cora. The casting of MacLaine was announced just last week and should serve to ramp up interest even further. Noted Sarah Ball, deputy editor of VanityFair.com, "There has been a tremendous online response. PBS does historically have an older audience, but 'Masterpiece' has courted that online fan base. They organized the live tweeting, put up sideshows and extras that really appeal to fans. It is interesting that a show set in 1917 happens to have such a rapid online fan base."