The longest-running science fiction show in television history, English import "Doctor Who" celebrates 50 years this week.
Relaunched in 2005 to great critical acclaim in its native England, the new series was sleek and modern with higher production values than it had ever known. Not bad for a show that was once relegated to PBS reruns and known for its low-budget charm.
Since then, "Doctor Who" has become a pop culture force around the world and has seen its popularity in the United States soar in recent years with Matt Smith in the title role of the Doctor.
One of the show's strengths is its ability to constantly welcome new viewers despite its 700-plus-episode history.
Don't know your Cyberman from your TARDIS? Here's a list of the 11 things - one for each of the Doctor's reincarnations - you need to know heading into the anniversary.
1. It's the 50th anniversay
This is a big deal for any show. The longest running science fiction show in history - eclipsing "Star Trek" by far - will be seen by TV audiences in 75 countries around the world at the same time. It airs stateside on BBC America at 2:50 p.m. EST.
2. Eleven actors, eleven Doctors
Not unlike James Bond, there have been multiple actors to play the Doctor. Matt Smith currently stars as the 11th, taking over in 2009 from the 10th, played by David Tennant. The character is the same, just with a new body from a process called "regeneration."
3. Each doctor is different, but the same.
Regenerations can give the Doctor a different personality and a different body, but it's the same Doctor with the same memories. "Even if I change, it feels like dying. Some new man goes sauntering away, and I'm dead," he once said.
4. He's the last one of his kind.
The Doctor is a Time Lord, an ancient race from the planet Gallifrey. Because of the deadly events of the previously unseen Time War, which will be shown in the anniversary episode, the Doctor ended the war with deadly consequences to both his enemies and his own people.
5. He travels in time and space in a police box.
The Doctor doesn't travel in time and space in a sleek, futuristic jet. He prefers a ship that camouflages itself as a wooden police box that used to be commonplace in London in the 1960s. Oh, and it's bigger on the inside.