1x02 THE END OF THE WORLD Of course you shouldn't miss the pilot which is all silly and funny but really, this is where it all begins. At the end of the world 500,000 years into the future and everyone's (everyone that is an alien) partying to give the dying planet a proper send-off. Proper meaning to Britney Spears' Toxic. Really! We meet Cassandra, the last human on Earth (Moisturize me!), and a colorful bunch of aliens who wouldn't get lost in a Star Trek or Star Wars or LoTR set. Rose (Billie Piper) makes it clear that she is the heart of the show and a wobbly attraction is implied between her and the Doctor (Christopher Eccleston). But just as Earth is about to blow up, the shields fail. You know how it ends but the writing is beginning to find its footing: Subtle characterization in bits and pieces, quirky humor, foreboding extinction.
1x04-05 ALIENS OF LONDON/WORLD WAR THREE A spaceship crashes into Big Ben. The Slitheen, much like the Teletubbies only vomit green, and Harriet Jones make their first appearance. This two-parter is a little too cutesy for me but it makes good use of supporting characters Mickey and Rose's mum, Jackie. Also, the series will keep referring to the incident that took place in these episodes. And yeah, a spaceship crashes into Big Ben.
1x06 DALEK The first appearance of the Dalek! One Dalek. The last of them. First mention of the Last Time War and how Time Lords and Daleks alike were wiped out of existence. Dalek climbs the stairs. Dalek launches into the air. Dalek exterminate, exterminate, exterminate! Dalek opens its shell and its not a pretty sight. Surprisingly heartbreaking ending. Again, the series will often refer to the repercussions of Rose's contact with the Dalek so you gotta see this.
1x09-10 THE EMPTY CHILD/THE DOCTOR DANCES London, 1941. A virus spreads that turns the infected's face into a gas mask. Turns. Your face. Gas mask. And on the other side of town, a ghostly kid, also infected, searches for his mum: Are you my mommy? all over town and coming out of every receiver. Creepy stuff. Great writing with tender moments in between scares and chases. This also marks the first appearance of John Barrowman as the irresistibly charming (to all genders and species, I think) Captain Jack Harkness. One of the best arcs and one of the more satisfying mysteries ever of the series.
1x12-13 BAD WOLF/THE PARTING OF WAYS In episode 7, The Long Game, the Doctor and Rose travel 200,000 years into the future and changed the oppressive politics of a broadcasting station. Good? Not really. Never mess with the butterfly. They fucked up the future big time and an enemy once thought extinct comes back with a vengeance. And a gazillion ships. If you've been watching TORCHWOOD, then this is where everything changes for Capt. Jack. And dear sweet Rose toys with being a god. Astonishing effects. Tight writing. Extremely suspenseful. And someone dies. Then regenerates into David Tennant.
* All images from Doctor Who at Scifi.com