"Downton Abbey" actors Dan Stevens and Michelle Dockery have become familiar in many countries. Nick Briggs / Carnival Film & Television for Masterpiece

Not long ago the actor Jim Carter replaced the crisp butler's uniform he wears on "Downton Abbey" with a Lycra ensemble for a cycling trip in Cambodia. Shooting had ended on the third season of the PBS "Masterpiece" series, and he celebrated with a ride along the Mekong River. Amid the temples of Angkor Wat he found himself wilting in the steamy climate - and swarmed by a group of Asian tourists screaming, "Mr. Carson!"

"Downton Abbey," an absorbing if somewhat formulaic costume drama set in the early decades of the 20th century, surprised even its architects by becoming a transcendent hit in both Britain and America. "Nobody in their right mind could have predicted what happened, when it sort of went viral," Julian Fellowes, the creator and the writer of the show, said in an interview. (The new season started in the United States on January 6.)

But perhaps even more surprising, the series, a quintessentially British dramedy, has also become a hit in Sweden, Russia, South Korea and the

Middle East. Since its September 2010 premiere in Britain, the show has appeared in more than 200 countries or regions, suggesting that anxiety about status and familial obligations - and a weakness for melodrama - observe no geographic bounds.

"Although in one sense," Mr. Fellowes said, " 'Downton' is very British - it's very fixed in a particular part and way of life, a particular limited range of society and so on - I think most of the stories are about emotional situations that everyone can understand."

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It has also been one of the most watched imports in Australia, Norway, Belgium, Israel and Iceland, according to Amandine Cassi, the head of international television research at Eurodata TV Worldwide, an audience-research company based in Paris.

NBC Universal International, owner of Carnival Films, which co-produces the series with "Masterpiece," estimates that more than 120 million viewers worldwide have watched the show. That number should grow significantly when CCTV in China begins offering a version dubbed in Mandarin this year, although some of the country's viewers are already well versed in "Downton."

"I was in Shanghai earlier this year and people were coming up to me saying it was their favorite show," said Gareth Neame, managing director of Carnival Films, who came up with the initial idea for the series. "This is the People's Republic of China, and this is a show all about primogeniture and inheritance and aristocracy and all those things that you thought the whole point of China was to do away with."

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The producers say the show resonates so deeply because of the universality of themes like the tensions of social status and, most important, the unabashed romance.

"The romance is depicted in a very sort of genuine, heartfelt way," said Mr. Neame, an executive producer. "And we've found that no matter where you live on this planet, you get it."

Mr. Fellowes added, "You travel thousands and thousands of miles, and you get off the plane, and someone says, 'Is Mr. Carson going to marry Mrs. Hughes?' "