The Doctor, played by William Hartnell, turns out to be an alien time traveller. He whisks the teachers away on an adventure in time and space. The magic of the show is evident from the very first notes of the terrifying theme music, making this an obvious starting point.
Now obviously "An Unearthly Child" -- broadcast on 23 November 1963 -- is from a very different time. The TV of yesterday looks quite quaint to our eyes, but even so there's mystery, charm and often a genuinely sinister edge to early "Who".
"Remembrance" is "Who" firing on all cylinders: an all-action plot with explosive special effects, new companion Ace creating the template for today's no-nonsense sidekicks, and a subtle call-back to the show's storied history.
"The Tenth Planet" was also the final adventure starring William Hartnell as the Doctor. Instead of ending the show, the creators hit on the novel concept of using our hero's Time Lord physiology to explain a transformation into a new body, a process now known as regeneration. The second Doctor was played by Patrick Troughton.
Now we're talking. Considered by many fans to be the finest "Who" adventure ever, "Genesis" sees fourth Doctor Tom Baker arrive at the inception of his greatest enemy to face a mortal moral choice. The philosophical depth of the story perfectly shows why the Doctor is such a compelling character, using intelligence and compassion to defend against evil.
In season 10, the Doctor seems to have given up wandering in time and space for a post at a university. Only once before has the Doctor settled in one place, when he was banished to Earth for third Doctor Jon Pertwee's swashbuckling tenure. "The Daemons" is one of the best stories of this excellent era.
Luckily for us, adventure was never far away: it seemed like every week evil lurked in a quaint English village, where the Doctor and his alien-fighting military chums UNIT must save the day. Meanwhile, as in the current show, the Master was never far away...
Longest-serving Doctor Tom Baker takes on an terrifying alien menace in fog-shrouded Victorian London in this much-loved serial. In many ways it encapsulates "Who": the Tardis arrives in a historical setting, rendered with the peerless period expertise of the BBC; it includes both sinister villains and engaging secondary characters worthy of their own show; and classic story tropes -- in this case from "Sherlock Holmes", "Fu Manchu" and "The Phantom of the Opera" -- given an exhilarating sci-fi twist.
Season 10 will feature classic aliens the Ice Warriors in a story set on their home planet of Mars, written by Mark Gatiss. In their earlier stories the Ice Warriors were depicted as menacing monsters, but the 1972 serial "The Curse of Peladon" subverts and transcends such simplistic storytelling.
It's only fair to mention each of the original seven Doctors, so we've thrown in this 1985 political satire to represent Colin Baker's sixth Doctor. But between you and me, it's OK to turn this off and watch a Tom Baker one instead.