Season 16

The sixteenth season of Doctor Who ran between 2 September 1978 and 24 February 1979. It consisted of six serials and twenty-six episodes. This season saw the introduction of the Black and White Guardians as well as the companion Romana I. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured ), it was the first to be recognised as having a series-long arc. Although multi-serial arcs would occur again, such a full-season experiment wouldn't be attempted again until Season 23.

Season 16 marked a triple milestone for Doctor Who: the hundredth story (The Stones of Blood), the five-hundredth episode (episode 1 of The Armageddon Factor) and the fifteenth anniversary of the first broadcast, on 23 November 1978.

A number of publicity photos for the season show Tom Baker sporting a very obvious bandage on his upper lip; this was due to his being bit by a dog shortly before filming for the season began. The resulting lip injury is visible to varying degrees throughout the season.

In 2002 (Region 1) it became the first Doctor Who season to be released to DVD in its entirety in a single box set; it remained the only "classic series" season to be available as a single set until the release of Season 23, The Trial of a Time Lord to DVD in 2008.

Recurring

 * The Fourth Doctor - Tom Baker
 * Romana I - Mary Tamm (introduced The Ribos Operation)
 * K9 - John Leeson (voice) (absent during The Power of Kroll)

Stories set during this season

 * PROSE: Tomb of Valdemar (between The Ribos Operation and The Pirate Planet)
 * PROSE: The Shadow of Weng-Chiang (between The Stones of Blood and ''The Androids of Tara)
 * PROSE: Heart of TARDIS (between The Stones of Blood and The Androids of Tara)
 * AUDIO: Ferril's Folly (between The Stones of Blood and The Androids of Tara)
 * PROSE: X-Rani and the Ugly Mutants (between The Androids of Tara and The Power of Kroll)
 * PROSE: Light Fantastic (between The Androids of Tara and The Power of Kroll)
 * PROSE: Reluctant Warriors (between The Androids of Tara and The Power of Kroll)
 * COMIC: The Weapon (between The Androids of Tara and The Power of Kroll)
 * PROSE: Return of the Electrids (between The Androids of Tara and The Power of Kroll)
 * PROSE: The Sleeping Guardians (between The Androids of Tara and The Power of Kroll)

VHS

 * The Ribos Operation
 * The Pirate Planet
 * The Stones of Blood
 * The Androids of Tara
 * The Power of Kroll
 * The Armageddon Factor
 * The Tom Baker Years (excerpts from all stories)

DVD
This entire season was released with minimal restoration and extras in region 1 only on 1 October 2002 as a box set and was available individually. A limited edition box set with full restoration and expanded extras was released in region 2 on 24 September 2007. This limited edition version was later issued as the 7 November 2007 region 4 release, the 3 March 2009 region 1 "Special Edition" release (these were also available individually), and the 16 November 2009 non-limited region 2 re-release.

Novels
Target Books was unable to come to an agreement with Douglas Adams to novelise his script, The Pirate Planet, leaving it one of only a half-dozen classic-series episodes never adapted as a book.
 * Doctor Who and the Ribos Operation
 * Doctor Who and the Stones of Blood
 * Doctor Who and the Androids of Tara
 * Doctor Who and the Power of Kroll
 * Doctor Who and the Armageddon Factor