The Doctor is a Time Lord, which is a long-dead race of people who were responsible for ensuring that time wasn’t altered or abused. The entire race was wiped out in the Time War with the Daleks (who my friend Brooke affectionately refers to as “The Trashcan Monsters”). The Daleks hate everything that isn’t a Dalek and their ultimate goal is to wipe out every other race in the universe.
One of the themes in the show is that The Doctor himself was responsible for wiping out both races in order to end the war, and has lived with that burden for over 900 years. But wait, weren’t they wiped out? Yes, but due to multiple timelines, some survived in various ways so they’re still working on either killing or converting every living species into more Daleks.
In order to keep the show running back in the 60’s, after the original actor left, producers had The Doctor “die” and regenerate into a new body. This is why there have been so many people who’ve played The Doctor over the years. Each time the character regenerates, he has a new body and face, and has to figure out what kind of person he is. The show is currently on its eleventh Doctor, played by Matt Smith. Same man, new face and personality.
The first episode I watched was Blink, which ironically features very little of The Doctor himself. However, the episode illustrates very well the idea that he’s a time traveler and sometimes overlaps his own lifetime, meeting people who know him before he’s actually interacted with them. (How’s that for a mind twist?) The episode is also totally creepy, and introduces the Weeping Angels, arguably one of the best villains of the entire show. This is also where the phrase “Don’t Blink” originated.
Even if you haven’t watched Doctor Who in years, you can still catch up with it easily. Many of the episodes stand alone or are two-parters, and while it helps to know who the monsters are and to follow the series chronologically, you can still enjoy it without a lot the back story. Much of it is easy to pick up as you go along.
The Doctor almost always travels with a companion, some willing and some thrown into the story with very little choice. Usually, The Doctor will travel with the same companion(s) throughout his tenure on the show, with a few exceptions. They all bring something unique to the story though, and every fan has their favorites or that one companion they just can’t stand.
Doctor Who doesn’t dumb anything down for you. The Doctor is intelligent, his companions are intelligent in their own ways and the show assumes its audience is intelligent too. The writers leave clues littered around for you to pick up on throughout each season, making it the ultimate show for smart people. Many themes are repeated throughout multiple seasons and the writers are masters of the “callback”, referencing prior characters and themes.
There’s a very palpable underlying pathos to the overall storyline, as you watch The Doctor have to deal with his past, his guilt and losing people he cares about. But laid over top of that are a lot of fun one-liners and witty humor that makes the show extremely entertaining to watch. If you’re a sci-fi fan and haven’t watched any of it, I recommend giving it a shot.