Imagine, just for a moment, worlds beyond this one. Imagine hundreds of planets, hundreds of galaxies. Imagine planets with names like Skarro, and Traken, and Gallifrey -- planets with beings more evil than you can imagine and more amazing than you can imagine. Imagine a society held together, by, in one man’s words, “people basically being very very nice to each other.” Imagine a type of species with no heart, no morals, no conscience.

Now, imagine parallel universes, all stacked up next to one another. A universe in which there are men with frozen hearts and a body of steel, worlds with “ultimate upgrades” and people who died long past still alive.

And now, imagine a man with two hearts, a man who isn’t quite a man. A man with no name, just a title. A man who can change his face with as much ease as people change clothes, a man who travels through all of time and space in a blue police box… a man who will take you along for the ride.

That’s Doctor Who. The premise is simple. A man -- or, rather, an alien, called the Doctor, from the planet Gallifrey. A Time Lord, equipped with a time machine -- the TARDIS (Time And Relative Dimension In Space), who travels all of time and space, picking up people along the way, saving alien planets and Earth alike. A man who can regenerate when he’s dying, changing his face, and, conveniently replacing the actor. A man who fights, and wins, not using guns or swords or violence, but just his mind. And he always wins. It’s one of the rules.

But by the end of the legendary British sci-fi’s show run, it had turned into less of a legend and more of the regular, stock-trade sci-fi with bad special effects if good plot lines. And in the 1980’s, it was discontinued.

Until Russell T. Davies came along, with clever new twists and a brand-new, war-scarred Doctor, faced by Christopher Eccleson as the Ninth Doctor. But this wasn’t just some sci-fi show. Because behind the quick words and quicker wit, there was something deeper. Darker. A touch of reality. In the first season’s finale, the Doctor is forced into the 2002nd century, into a game. A reality TV show, Big Brother. But this time, if you’re evicted, you’re evicted from life. And the whole world’s watching, because they can’t go outside, it’s too dangerous to breathe, because of the ozone. Between escaping from the game and fighting the Daleks (his worst enemy), he says, “Half the world’s too fat and the other half’s too thin.” You ignore it then. But then you think. And you know this might happen. If we’re not careful. We’re getting closer and closer every day.

Then David Tennant comes, as the Tenth Doctor. A wild, laughing, slightly manic Doctor, who can’t help but laugh and joke in the face of evil, and often does. A Doctor who wants to be ginger and doesn’t give people second chances. A kind, passionate Doctor -- but not necessarily a nice one. A Doctor who, when asked what monsters under the bed have nightmares about, smirks and says, “Me!” A Doctor who never uses a gun, who orders everyone to put their guns down -- who’s only armed with a sonic screwdriver, who never fights, and still manages to save the world every time, with a sonic screwdriver, his wits, and the people he picks up along his journeys. A Doctor who quotes Back to the Future and, when asked how come he doesn’t know about Utopia, replies he’s a bit of a hermit, and when asked about his friends, shrugs and says, “Hermits united. We meet up every ten years, swap stories about caves. It's good fun. For a hermit.” Who always wins, no matter how bad it looks. And who never, never kills, whether he’s facing psychopathic Time Lords that destroy the world listening to the Scissor Sisters, or Daleks, creatures with no heart and no morals and no purpose but to “Exterminate!”

And we’ve had him for three years, and each one has been, in the Ninth Doctor’s words, “Fantastic!” It’s quickly become one of the most well known sci-fi shows in England, and in the US. It’s won over twenty awards in five years, and keeps on winning more and more.

It’s run for 45 years, and through the years, it’s gotten smarter, quicker, and, occasionally, darker. But always fantastic, whether the Doctor is the first -- an old, slightly strange man, or the Fourth, with his inanely long scarf, or the Sixth, with a “coat of many colors,” or the Tenth, with his red converse and sarcasm. Because he’s the Doctor, no matter how he looks or dresses or what he says, at the heart of it, he’s still the Doctor.

45 years.

219 stories.

Ten Doctors.

One legend.