The BBC introduced England to the doctor on Nov. 23, 1963. Every week on "Doctor Who," the science fiction adventurer traveled through space and time in his Tardis, a ship disguised as a blue police call box.
The doctor became an institution during the next five decades, but it took some time for "Doctor Who" to catch on across the pond.
As the show's 50th anniversary approaches this weekend, it's clear the doctor has made the leap. The United States has become one of the biggest markets for "Doctor Who" since the show's relaunch in 2005. BBC Worldwide has leveraged its growing popularity, driving up the brand's value through home entertainment sales and revenues from an array of collectibles, clothing and events.
The series ran in the U.K. from 1963 to 1989. A TV movie in 1996 was an attempt to reboot the show and appeal to Americans by casting lots of Yank actors. That failed. But "Doctor Who" relaunched in 2005 once-again as a British-centric show, and that did the trick.
Today, "Doctor Who" is the top performer on the cable channel BBC America and only getting stronger. Viewership rose 51 percent in the year ending in March, according to the BBC's 2013 Annual Report.
The BBC won't break out revenues generated by "Dr. Who" but did say it is among BBC Worldwide's three biggest franchises, along with "Top Gear" and "Dancing with the Stars."
Clearly, the show's success has helped boost BBC Worldwide revenues. For the year ending in March, U.S. revenues reached $550 million, a significant portion of its $1.8 billion in global annual sales. The BBC America channel expanded audience by 4 percent, to 80.6 million homes.
BBC Worldwide is the for-profit arm of the U.K.'s subsidized BBC. The main part of its business is licensing BBC content overseas through channels such as BBC America.
Ratings don't tell the whole story, though. Thanks to a loyal fan following, "Doctor Who" is highly visible in social media, regularly registering as a trending topic on Twitter and taking the top spot on Tumblr.
" 'Doctor Who' may not get the audience of 'NCIS,' but it certainly resonates more," said Herb Scannell, president of BBC Worldwide America. "There's deeper engagement. There's a loving audience that engages with it when it's on television and when it's not."
(Read more: POW! Superhero films knock 'em dead in China)
In the U.K., he said, parents and children tend to watch "Doctor Who" together, while the U.S. audience consists primarily of a generation of young comic book and science fiction fans.
American fans discover "Doctor Who" on their own or by word of mouth, said Soumya Sriraman, executive vice president of home entertainment and licensing for BBC Worldwide North America.
"We're seeing that a lot of this is coming from young girls, who are coming into the franchise and bringing others into it," said Sriraman. "It's a very interesting trend."
Capturing science fiction enthusiasts has paid off for BBC Worldwide. "Doctor Who" became the sixth-most valuable TV brand in the United States this year, according to BBC analysis of Nielsen VideoScan data.
In addition to DVDs, BBC Worldwide and its licensees offer everything from action figures to Tardis-shaped minirefrigerators. One of the most popular items is a $100 replica of the doctor's signature accessory, the sonic screwdriver. An average 1,000 are sold every day, Sriraman said.
Besides a global television broadcast of a 50th anniversary special, the BBC is releasing the same special, "The Day of the Doctor," in theaters in 11 markets at the same time.
(Read more: Netflix's Reed Hastings takes a new approach)
U.S. presales for "The Day of the Doctor" theater screenings have exceeded all expectations, said Kurt Hall, CEO of NCM, the BBC Worldwide's marketing partner.
NCM has sold about 175,000 tickets, a record for the company, and has expanded the number of theaters to 645 from an initial list of about 300. With tickets priced at about $12 to $14, U.S. pre-sales likely have exceeded $2 million for the Saturday afternoon and Monday night shows.
"It's been unprecedented," Hall said. "All marketers pray for this, but you can never tell if it's going to happen."
Most of the screenings are sold out, but American fans are also gathering at local establishments to watch the anniversary special on the small screen.
The Way Station, a science fiction-themed bar in Brooklyn, N.Y., expects such a large crowd that it arranged for four neighboring bars to accommodate the overflow by showing "The Day of the Doctor."
"The response has been amazing," said Andy Heidel, The Way Station's owner. "People are just coming out of the woodwork and foaming at the mouth to watch the 50th anniversary here."
Scannell at BBC Worldwide America said that though the company has actively cultivated the U.S. fan base, he ultimately chocks up the show's success to solid storytelling and a rich fantasy world that draws in viewers of all nationalities.
(Read more: Why and how the 'Breaking Bad' finale broke records)
"There are not many shows you can literally play around the world, that can unite the world," he said. "This is one of them."
—By CNBC's Tom DiChristopher. Follow him on Twitter @tdichristopher.
—An earlier version of this story incorrectly spelled Kurt Hall's name.