K9

for the TV series see K-9 (TV series)

"Affirmative, Master"

- K-9

K-9 is the designation given to a series of intelligent dog-like androids who have served as companions for the Doctor, Leela, Romana and Sarah Jane Smith. The robots' name is often presented as K9 with no hyphen (The Adventures of K9).

K-9 Mark I
"Ready, master."

- K-9 to the Doctor Professor Marius invented the first K-9 because weight requirements did not allow him to bring his real dog from Earth into space (DW: The Invisible Enemy) though K-9 may owe his existence to a temporal paradox. According to one account, the professor copied the remnants of one of the version of K-9 created by the Doctor and given to Sarah Jane Smith. (DWM: Tautology)

The Professor offered K-9 to the Doctor as the same weight requirements made him unable to take Mark I back to Earth with him. (DW: The Invisible Enemy) After a number of adventures with Leela and the Doctor, Mark I decided to stay on Gallifrey with his "mistress". (DW: The Invasion of Time). ''The Fourth Doctor and K-9 Mark II spent an indeterminate period of time together. However, in the next episode, DW: The Ribos Operation, the Doctor appeared to be activating K-9 Mark II, giving the implication only that no significant time had elapsed since leaving Gallifrey.''

There are (possibily apocryphal) accounts that this model of K-9 later performed missions on behalf of the Time Lords and was given control of a space vessel called K-NEL (The Adventures of K9: K9 and the Time Trap, et al).

K-9 Mark II
"Optimism: belief that everything will work out well. Irrational, bordering on insanity"

- K9 on optimism

At some point prior to this, the Doctor obtained or constructed at least one (possibly more) backup models of K-9, and immediately after leaving Mark I behind with Leela, the Doctor unpacked K-9 Mark II. This version of K-9 accompanied the Doctor and new companion on their quest to locate the segments of the Key to Time (DW: The Ribos Operation), however the swampy terrain of Delta III made it impossible for him to accompany them there. At the conclusion of the quest, the Shadow turned K-9 to his evil will, during which time K-9 assumed a sinister personality. (DW: The Armageddon Factor)

The Doctor found that K-9 had contracted laryngitis and had lost his voice as a result of this. K-9 was left in the TARDIS while the Doctor and Romana battled the Daleks and Davros (DW: Destiny of the Daleks). During a subsequent adventure, it remained patiently in the TARDIS, which would imply that his voice had not yet returned. (DW: City of Death) After the return of his voice, it sounded quite different and remained so for a number of adventures (DW: The Creature from the Pit). However, later the familiar voice returned. (DW: The Leisure Hive)

Damaged by the time winds, K-9 Mark II could not cross back into N-Space with the Doctor, so decided to stay behind at the Gateway with Romana, to help her free the remaining Tharils from slavery. (DW: Warriors' Gate) Eventually, however, Romana and the presumably repaired K-9 returned to their own universe, and K-9 Mark II came to live on Gallifrey. (NA: Lungbarrow, WC: Shada)

The fates of K-9s Mark I and II in light of the Last Great Time War remain unknown.

K-9 Mark III
"K-9! Rose Tyler, Mickey Smith, allow me to introduce K-9! Well, K-9 Mark III, to be precise."

- The Tenth Doctor introducing K-9 to Mickey and Rose

A third model, K-9 Mark III (again either obtained or constructed by the Doctor) was given in the late 1970s to Sarah Jane Smith to serve as Sarah Jane's companion for an indeterminate period of time. (KAC: A Girl's Best Friend) K-9 assisted Sarah Jane in defeating the Hecate worshippers of Moreton Harwood. (KAC A Girl's Best Friend) Circa 1983, K-9 Mark III still lived with Sarah Jane, but, by chance, did not accompany her to Gallifrey. (DW: The Five Doctors) K-9 accompanied Sarah to an archaeological dig in Egypt. (DWM: City of Devils) In the early 1990s, K-9 assisted Sarah in investigating a supposedly haunted house. (VD: Housewarming)

In 1996, Sarah used K-9 to hack into records and find Sam Jones' home address, and later to translate Lost Boy's speech. (EDA: Interference - Book One) K-9 was briefly possessed by a malevolent entity, but was freed when Sarah accidentally electrocuted him. (ST: The Sow in Rut) K-9 began slowly breaking down and eventually ended up deactivated in a cardboard box in Sarah's attic. (VD: Moving On) Hilda Winters had K-9 dismantled and analysed. (BFSJS: Mirror, Signal, Manoeuvre)

Sarah, unable to find anyone to fix the robot, continued to carry K-9 in the boot of her car, until a chance encounter with the Doctor in the mid-2000s resulted in K-9 being restored to functionality. This served to be only temporary, however, as Mark III destroyed itself in order to help the Doctor and his companions defeat a Krillitane invasion (DW: School Reunion).

K-9 Mark IV
"There was a scientific experiment in Switzerland, they created their own black hole. If it gets free the Earth will be swallowed up. So K-9 is sealing it off."

- Sarah Jane Smith

After Mark III sacrificed himself to defeat the Krillitanes, the Doctor left a new model, Mark IV, for Sarah Jane Smith, just seconds after he departed in his TARDIS (It's not known if the Doctor quickly built Mark IV from scratch or had it in storage). K-9 refers to himself as being rebuilt and improved, suggesting Mark IV possesses the same memory as Mark III. (DW: School Reunion) Though Sarah Jane didn't find this out right away, the Doctor had also placed some gifts in a panel in K-9's side: sonic lipstick and a Scanner Watch that could detect alien life.

A year before Sarah Jane first met Maria Jackson, K-9 Mark IV left Sarah Jane in order to stabilize a dangerous artificial black hole in space which had been created in Switzerland. He could only speak with Sarah occasionally via a cabinet with a spacetime link when the orbit of the black hole intersected with that of Earth and did not know when he would complete the job. (SJA: Invasion of the Bane) However, at times he was capable of returning to Earth briefly, and did so on two later occasions in order to render vital assistance. In the first time, he fought Mr Smith in pitched battle to allow Sarah to upload the Armaggedon Virus, (SJA: The Lost Boy) And again in order to quickly upload the Doctor's TARDIS' base code to Mr Smith and assist the Doctor in returning the Earth to its correct location in space. (DW: Journey's End)

After these events he went back monitoring the black hole only to find an unidentified member of the Slitheen family attempting to steal him as part of a revenge plot against Sarah Jane, who had foiled their plans in the past. K-9 banished the Slitheen, after reversing one of its attacks.(SJA: From Raxacoricofallapatorius With Love)



Personality
"The small female is hostile."

- K-9 on Kelsey Harper

K-9 had a very consistent personality from model to model. He had a polite, formal manner with just a hint of pedantry bordering on condescension. Though he often displayed feelings such as sorrow (DW: The Invasion of Time) and self-regard (DW: School Reunion), he often stated that he had not been programmed to have emotions (SJA:Invasion of the Bane.

He did not use contractions just as "you've" for "you have" and addressed others by titles such as "Master", "Mistress", "Doctor-Master" (to refer to the Doctor) or "Young Master" (Adric and in one instance Clyde). Though he did not seem to resent his subordinate status, he tended to side with the Doctor's companions over the Doctor himself and at times showed a dark side, regarding other artificial intelligences with contempt (DW: The Invasion of Time) and relishing a brief chance to act as a figure of power (MA: The Well-Mannered War) He usually did not engage in computer-like literal thinking, though on one occasion he followed Romana's instructions to "forget it" to the letter and erased all his knowledge of tennis from his memory banks. (DW: The Stones of Blood)

Because of him having great intelligence, he likes to board people with facts and does not immedinately stop when asked as he did to Leela on Pluto. When being told that he would have to stay behind in the TARDIS, K-9 would often argue giving the Doctor reasons why he should go such as "he would be a good dog." This shows K-9's willingness to assist the Doctor. He also has showed to have great intellegence and skill at chess as he was able to beat the Doctor in six moves (This may only be becuase he is programmed with all chess games since 1886.) (DW: The Sun Makers, The Androids of Tara) K-9 has revealed to have a aggression mode. (DW: State of Decay)

Features
"Oi! Listen, in the year 5000, this was cutting edge!"

- The Tenth Doctor

The mechanics of K-9 Mark I included rotating ear-probes, telescopic 'eye' probe, extendable nose, flashing lights on the top and the 'eye' panel, waggling tail antennae, and ticker-tape tongue. The head could also move up and down. The shell was painted in gold/grey metallic. Around K9's neck was a tartan collar, from which hung a silver disk. (DW: The Invisible Enemy)

After K-9 Mark I was left behind with Leela on Gallifrey, The Doctor built a improved K-9 Mark II. While the cosmetic changes were minimal (including the new metallic charcoal paint-work), in terms of series continuity K9's character underwent a vast change. Gone was the product of 5000 AD technology, as was the case with Marius's version. This new K9 was a product of the Doctor's own technology and values. The gun was now only capable of stunning - not killing - and K-9 now responded to a dog-whistle. K-9 also featured a vast memory-bank, seemingly a mixture of the Mark One model, the Doctor's own memory and knowledge, and that of the TARDIS. (DW: The Invasion of Time)

"Why does he look so... disco?"

- Rose Tyler on K-9 Mark III

When the Doctor left Sarah Jane Smith on Earth, he created K-9 Mark III to be Sarah's new companion. The new mechanics of K-9 Mark III included larger wheels in conjunction with a front and back-wheel drive. (K-9 was given a brand new coat of paint (this time a metallic-blue) plus a handle on the top of the shell to make carrying him easier. (KAC: A Girl's Best Friend)

When the Doctor created K-9 Mark IV to replace K-9 Mark III, he added a shiny metallic blue paint job and a number of improvements over Mark IV including an omniflexible hyperlink facility. (DW: School Reunion) Later, though, K-9 reverted to his old, dark green color. (SJA: Invasion of the Bane) In episode 2 of The Lost Boy Sarah Jane unleashes K-9 Mark IV to battle Mr Smith. Before and after the battle K-9 displays a teleport facility and utilises a laser weapon similar to the previous K-9s'. (SJA: The Lost Boy)

Marks
thumb|200px|right|[[The Doctor and K9 are engaged in a pleasant game of chess.(DW: The Sun Makers)]]
 * K-9 Mark I left behind with Leela on Gallifrey.
 * K-9 Mark II left behind with Romana in E-space.
 * K-9 Mark III left behind with Sarah Jane Smith on Earth.
 * K-9 Mark IV a new body for Mk III when it was destroyed in a Krillitane invasion.

Behind the Scenes
thumb|200px|left|K-9 Mark II blows up at the beach.
 * In an interview, the writers originally wanted to name K-9 "Pluto", after the Disney character; however, Disney refused permission.