Phone booths have become obsolete — except for the one used by a kindhearted alien to hurtle through time and space on his never-ending campaign to give peace a chance.

“Doctor Who,” which debuted 50 years ago as a low-budget children’s show, is celebrating its milestone birthday with a made-for-TV movie Friday about the show’s creation, a game-changing new episode Saturday and a barrage of fan accolades usually reserved for Jedi knights and crew members of the USS Enterprise.

Although the show draws 77 million viewers around the world, only about 1.5 million people watch the series on BBC America, but it’s a loyal base that forms fan clubs, creates Who-themed cocktails and storms conventions. At this year’s national Comic-Con, an annual celebration of everything from Fantasyland, the show’s current Doctor, actor Matt Smith, dressed like Bart Simpson to avoid being mobbed.

“I think it’s the closest thing to being a rock star,” Smith said.

Tickets sold out long ago to a big-screen, 3-D showing at AMC Southdale in Edina of the 50th anniversary episode Saturday afternoon, at the same time it premieres on TV. More local theaters will reprise the 3-D screening on Monday.

And then there’s the highly anticipated follow-up episode that will usher in a new Doctor on the night of Dec. 25.

“Some people go to church on Christmas, I watch ‘Doctor Who,’ ” said Diana Rajchel, a Twin Cities fashion blogger who runs a local fan club that boasts 780 members. The club will host a flurry of events Saturday at the Parkway Theater in Minneapolis, including a trivia bowl and a costume contest.

Rajchel, 38, got hooked on the series when she was 11 as a bonding experience with her father, who let her stay up past her bedtime to watch the show on Chicago public TV.

Life was cheap

During the first 26 years, the show looked like it was constructed in a garage. Minneapolis musician Christian Erickson, 43, remembers an episode in which a planet was represented by a moldy grapefruit hanging from a string.

But the not-so-special effects turned out to be part of the show’s charm.

“What they lacked in money they made up for ingenuity,” said Erickson, who has written “Dr. Who”-inspired tunes for his rock bands Astronaut Wife and Blue Sky Blackout. “Slick, glossy, shoot-’em-up stuff is fun to watch, but it’s not as interesting. This was deep and more sophisticated storytelling. After a while, you stopped noticing it was low-budget.”

The series went off the air in 1986 and returned in 2005 with a higher-tech look, but it still operates under the principle that less is more. In fact, the Doctor does his best to avoid conflict, a sharp contrast to other sci-fi heroes who wave light sabers first and ask questions later.

“Most of sci-fi focuses on war, but the Doctor tries everything else before he starts a fight,” Rajchel said. “That appealed to me even as a youngster.”

Another reason the show endured was purely accidental. William Hartnell starred in the title role for the first three seasons, but had to step down because of deteriorating health, a bittersweet story that’s the center of the made-for-TV film “An Adventure in Space and Time,” which premieres Friday night .

But the BBC wasn’t about to cancel a show that had 12 million fans, so the writers came up with a twist: What if the alien Doctor had the ability to regenerate himself a dozen times?

The chance to recast the lead every few years not only gave producers bargaining power come contract time; it also allowed the show to grow up along with its audience.

“It’s a way of not getting old,” said Aubry D’Arminio, a staff writer for TV Guide magazine, which is featuring the show on this week’s cover. “You’re able to dust yourself off and do a complete change.”

Not just for nerds

The idea of adapting to new faces and complex story lines may sound like a job for Supergeek, but D’Arminio insists that you’ll see all kinds of fans at conventions.

“I know there’s this idea that they are big dorks that do nothing but stay at home and watch TV,” she said. “But we’ve got a copy editor here that’s a huge fan and she looks like a model.”

Card-carrying Whovians do have one thing in common, Rajchel theorizes — a sense of curiosity.

“This is not a show that falls into your lap. You’ve always had to search for it,” she said. “I think fans have a higher sense of motivation.”

Those fans may also be feeling a higher sense of anxiety.

When Peter Capaldi takes over as Who on Christmas Day, he’ll be the 12th Doctor. Based on the original story line, that means he should be the next-to-last regeneration.

But head writer Steven Moffat hinted that he’s written himself a loophole, which is another way of saying he’s not about to close shop on a show that makes the front page of London newspapers when a new Doctor is announced.

Erickson said he’s thrilled that the show has remained on long enough to draw in his 12-year-old son, who discovered Who all on his own. But there’s a tiny downside: Erickson won’t be able to go to Southdale on Saturday night to watch the new episode on the big screen.

“I was looking forward to going to a geek fest, but I have to bow to my son,” he said. “He wants to have a kid-viewing party at the house with five or six of his friends.”

There’s a good chance “Doctor Who” will be around long enough that he’ll have the same conflict with his future grandchildren.