K9

K9 — occasionally styled K-9 — was the designation given to a series of intelligent, dog-like robots who served as companions for the Fourth Doctor, Leela, Romana, Sarah Jane Smith and Starkey.

K9 Mark I
Professor Marius, who invented the first K9, described him as "my best friend and constant companion." Marius had a dog on Earth, but weight requirements did not allow him to bring his real dog into space; he built K9. (DW: The Invisible Enemy) However, K9 might owe his existence to a temporal paradox. According to one account, the Professor copied the remnants of one of the versions of K9 created by the Doctor and given to Sarah Jane Smith. (BE: Tautology)

The Professor offered K9 to the Fourth Doctor as the same weight requirements made him unable to take Mark I back to Earth. (DW: The Invisible Enemy) After 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 K9 Mark II spent an indeterminate period of time together. However, the Doctor appeared to be activating K9 Mark II, implying that no significant time had elapsed since leaving Gallifrey. (DW: The Ribos Operation)

There are (possibly apocryphal) accounts that this model of K9 went on 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).

K9 stayed with Leela on Gallifrey for many years. It was only after the disappearance of her Time Lord husband, Andred, that Leela and her K9 met Romana and her K9. The two K9s did not get on well and competed. (BFG: Weapon of Choice) After Leela became Romana's bodyguard and after many important missions on her behalf, Leela's K9 was destroyed by an exploding bomb. Leela was heartbroken, but refused to have a duplicate unit built. (BFG: Imperiatrix)

However, K9 survived this and the Last Great Time War. He witnessed the murder of Zanthus Pia by Ahab. His Jixen henchmen fought him and were transported to 2050 Earth. K9 self-destructed to protect the humans nearby, then regenerated into a more advanced model. (K9TV: Regeneration,The Bounty Hunter)

K9 Mark II


Before this, the Doctor obtained or constructed at least one backup model of K9. Immediately after leaving Mark I behind with Leela, he unpacked K9 Mark II. This version of K9 accompanied the Doctor and his new companion on their quest to locate the segments of the Key to Time, (DW: The Ribos Operation) but the swampy terrain of Delta III made it impossible for him to join them on the planet. At the conclusion of the quest, the Shadow turned K9 to his evil will, giving K9 a a sinister personality. (DW: The Armageddon Factor)

The Fourth Doctor found that K9 had contracted laryngitis and had lost his voice as a result of this. K9 was left in the TARDIS while the Doctor and Romana II battled the Daleks and Davros. (DW: Destiny of the Daleks) During a later adventure, he remained patiently in the TARDIS, which would imply that his voice had not yet returned. (DW: City of Death) After his voice returned, it sounded quite different and remained so for a while (DW: The Creature from the Pit) before the familiar voice returned. (DW: The Leisure Hive)

K9 travelled to E-Space with the Fourth Doctor and Romana II, where they met Adric. He had his head knocked off while trying to defend Romana, Adric, Varsh, Tylos and Keera. (DW: Full Circle)

Damaged by the time winds, K9 Mark II could not cross back into N-Space with the Doctor. He decided to stay behind at the Gateway with Romana II to help her free the remaining Tharils from slavery. (DW: Warriors' Gate) Eventually, Romana II and the presumably repaired K9 returned to their own universe and K9 Mark II came to live on Gallifrey. (NA: Lungbarrow, WC: Shada, BFA: Zagreus)

During Romana's Presidency of Gallifrey, Leela became her bodyguard, and the two K9 units were forced to work together, not always amicably. After Matthias had replaced Romana as President, he nominated her to undertake a mission to find a cure for the Free Time virus, to be followed by exile. K9 opted to remain in the employ of Matthias, fighting the infection on Gallifrey. However, Braxiatel and K9 had planned another operation. Realising that the only cure to the virus was to end the regeneration capabilities of the Time Lords, Braxiatel used a Time Scoop to collect the Time Lord bio-data archive (along with K9). Romana was asked to decide whether to administer the cure or let Gallifrey die and rebuild it from scratch with the bio-data archive. Her decision is not known. (BFG: Gallifrey)

The fates of K9 in light of the Last Great Time War remain unknown.

K9 Mark III
A third model, K9 Mark III (again either obtained or constructed by the Doctor) was shipped to Sarah Jane Smith in 1978 to serve as her companion, but she did not receive his gift until 1981. K9 helped Sarah Jane defeat the Hecate Cult of Moreton Harwood. (KAC: A Girl's Best Friend) Circa 1983, K9 Mark III still lived with Sarah Jane, but by chance did not accompany her to Gallifrey. (DW: The Five Doctors) K9 accompanied Sarah to an archaeological dig in Egypt. (DWM: City of Devils) In the early 1990s, K9 assisted Sarah in investigating a supposedly haunted house. (VD: Housewarming)

In 1996, Sarah used K9 to hack into records and find Sam Jones' home address and later to translate Lost Boy's speech. (EDA: Interference - Book One) K9 was briefly possessed by a malevolent entity, but was freed when Sarah accidentally electrocuted him. (ST: The Sow in Rut) K9 began slowly breaking down and eventually ended up deactivated in a cardboard box in Sarah's attic. (VD: Moving On) Hilda Winters had K9 dismantled and analysed. (BFSJS: Mirror, Signal, Manoeuvre)

Unable to find anyone to fix the robot, Sarah carried K9 in the boot of her car, until a chance encounter with the Tenth Doctor in the mid-2000s resulted in K9 being restored to functionality. This was only temporary, however. Mark III self-destructed to help the Doctor and his companions defeat a Krillitane invasion (DW: School Reunion).

K9 Mark IV


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. K9 referred to himself as being rebuilt and improved, suggesting Mark IV possessed the same memories 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 K9's side: sonic lipstick and a scanner watch that could detect alien life.

A year before Sarah Jane first met Maria Jackson, K9 Mark IV left Sarah Jane to stabilise a dangerous black hole in space which had been created in Switzerland. He could only speak with Sarah Jane occasionally via a cabinet with a space-time link when the orbit of the black hole intersected with Earth's and did not know when he would complete the job. (SJA: Invasion of the Bane) However, he returned to Earth very briefly during emergencies. He did so on two later occasions in order to render vital assistance. The first time, he fought Mr Smith in pitched battle to give Sarah Jane time to upload the Armageddon Virus. (SJA: The Lost Boy) The second time, he quickly uploaded TARDIS base codes to Mr Smith, assisting the Tenth Doctor in returning Earth to its correct location in space. (DW: Journey's End)

After these events, he returned to monitoring the black hole. He emerged to find a member of the Slitheen family attempting to steal him as part of a revenge plot against Sarah Jane, as she had foiled their plans in the past. K9 banished the Slitheen after reversing one of its attacks. (SJA: From Raxacoricofallapatorius With Love)

K9 returned when Ship used the black hole as fuel. Though Sarah Jane, Luke, Rani and Clyde were happy to have K9 back, Mr Smith was not. (SJA: The Mad Woman in the Attic) K9 spent a lot of his time in Sarah Jane's attic at 13 Bannerman Road, but left to defeat Travist Polong. He attended Sarah Jane's wedding to Peter Dalton, where he helped the Tenth Doctor, Luke, Rani and Clyde defeat the Trickster. (SJA: The Wedding of Sarah Jane Smith) After helping defeat the Slitheen family, Clyde brought K9 to Park Vale Comprehensive School to help him with his test. He helped defeat the Rakweed before returning home. (SJA: The Gift) K9 went to the University of Oxford with Luke, but restored Mr White's original programming through a mobile phone.(SJA: Goodbye, Sarah Jane Smith)

In 2056, Sarah left K9 to a boy who would later help Drax search for the Sixth Doctor, who was being held captive by Omega. (FYF: Search for the Doctor)

Living art simulation
During an encounter with the sentient painting, the Mona Lisa at the International Gallery, a simulation of K9 Mk IV was created when Mona Lisa was tricked into animating a drawing of K9 made by Clyde inside a cloud of mystic drawing-animation energy. He subsequently defeated the Abomination, another evil painting-come-to-life, before disappearing as the Mona Lisa herself reverted to being an immobile painting. (SJA: Mona Lisa's Revenge)

K9 Mark 2


After Mark I sacrificed himself to destroy the Jixen warriors, Starkey retrieved his regeneration unit. K9 was rebuilt as a much more advanced model, but had no memories. He stayed at the house of Alistair Gryffen, who ran tests on K9, but did not tell the Department. K9 tried to kill Starkey, as he was sprayed with Jixen genetic matter and so registered as a Jixen. Starkey convinced him that he was not an enemy and K9 gave him his dog whistle to summon him when needed. (K9TV: Regeneration) K9 and the team tracked down the surviving Jixen to Dauntless Prison and killed it. They also faced a Meron and freed the alien prisoners. (K9TV: Liberation) K9 travelled with Starkey when he was on the run from the Department and rescued Gryffen (who was kidnapped by a Korven). Gryffen later welcomed him and Starkey into his home. (K9TV: The Korven)

Later he defeated Ahab, who tried to convince him he had murdered Zanthus Pia. He became part of the K9 Unit, being made the responsibility of Gryffen and under the control of Department inspector June Turner. (K9TV: The Bounty Hunter) He foiled Inspector Drake's plan to control the population using Cerulium (K9TV: Sirens of Ceres) and experienced fear. (K9TV: Fear Itself) He aided in the defeat of echoes of Gryffen's family, (K9TV: The Fall of the House of Gryffen) Orthrus, a duplicate of him created by Drake to frame him (K9TV: Jaws of Orthrus) and the Bodach. (K9TV: Dream-Eaters) He met Nehetka and Geb of the Anubians, a race his previous incarnation liberated. He was so obsessed with regaining his lost memories that he didn't notice Gryffen, Starkey and Jorjie's takeover by the Anubians. He soon found out when the Anubians attacked the Department. With Darius' help, he defeated them. (K9TV: Curse of Anubis)

He helped Starkey fight the Oroborus, (K9TV: Oroborus) free the Medes (K9TV: Alien Avatar) and help one of the last Aeolians find her mate. (K9TV: Aeolian) He saved a Centuripede and her young from being killed by Drake (K9TV: The Last Oak Tree) and absorbed the Hunger swarm which threatened to devour Earth. (K9TV: Black Hunger) Starkey and he went through the STM to 1963, where they rescued Jorjie and saved Darius' great-grandfather William Pike from arrest and Darius from erasure from history. (K9TV: The Cambridge Spy) He enlisted the help of the Ukkan librarian Yssaringintinka to rescue Starkey, trapped on the planet Urlic. (K9TV: Lost Library of Ukko) He helped Birdie, a CCPC whith implanted human DNA, escape from the Department. (K9TV: Mutant Copper) He discovered the last of the Etydions (K9TV: The Custodians) and taught Taphony how to be a friend. (K9TV: Taphony and the Time Loop)

Either Inspector Thorne or Lomax found out about K9's regeneration unit and decided to acquire it. Thorne joined forces with Freddie Maxwell, owner of Crashclub involving old robots being made to fight. K9 went undercover as a gladiator and made friends with the robot clowns Chuckles and Boris. He was called to fight the Pain-Maker, who was laced with the explosive solarmite. When he was set to self-destruct, K9 detected this and fled the explosion. (K9TV: Robot Gladiators) To regain his memory and find out his connection to the STM, K9's archive was scrambled. Directives from the STM almost caused him to self-destruct and lose all his memory. However, with Gryffen and Starkey's help he overrode the directives. (K9TV: Mind Snap) He helped Gryffen find the STM's temporal stabiliser from the fallen angel crash site in Canada, where it was revealed to be Korven technology. (K9TV: Angel of the North) He stopped haywire CCPCs when The Last Precinct's plan backfired. (K9TV: The Last Precinct)

After this he was tricked by Thorne to give him his regeneration unit for a lost memory chip/ This turned him into a bomb to make him self-destruct on encountering Jixey. Starkey helped him disarm himself. (K9TV: Hound of the Korven) K9 Mark 2's brief life was almost cut tragically short when after the fall of the Korven invasion force, Thorne sent the Trojan to kill K9, who defeated it by burning out his power core and exhausting all his energy. As his regeneration unit was in the Trojan, K9 seemingly died at the mansion after his companions bade him farewell. However his regeneration unit homed in at the last minute and resurrected him, giving the frisky pup a new lease on life. The regeneration unit restored his old dog collar so he could celebrate the joyful occasion to the full as he flew off to more adventures, bristling with life. (K9TV: The Eclipse of the Korven)

Personality
K9 had a personality very consistent across the models with some contact with the Doctor. He was polite and formal, with 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 such 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, Starkey and in one instance, Clyde). Though he did not seem to resent his subordinate status, he sided with the Doctor's companions over the Doctor and showed a dark side, regarding other artificial intelligences with contempt. (DW: The Invasion of Time, SJA: The Wedding of Sarah Jane Smith, K9TV: Robot Gladiators) He relished 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 knowledge of tennis from his memory banks. (DW: The Stones of Blood)

With his great intelligence, he had a tendency to bore people with facts and did not stop immediately when asked, as he did to Leela on Pluto. When being told that he would have to stay behind in the TARDIS, K9 often argued, giving the Doctor reasons why he should go such as "[he] would be a good dog." K9 always wanted to assist the Doctor. He had great intelligence and skill at chess, claiming to be able to beat the Doctor in six moves (although this may only have been because he was programmed with all chess games since 1886). (DW: The Sun Makers, The Androids of Tara) K9 had an aggression mode. (DW: State of Decay)

K9 Mark 2 had some obvious commonalities with the Mark I that had preceded him. However, as he had almost completely lost his personal memories, he was forced to reacquaint himself with the world around him. Toward this end, he downloaded thousands of human movies onto his memdrive, which peppered his speech with 20th and 21st century English colloquialisms that his "brothers" did not typically employ. (K9TV: Alien Avatar) Despite his negative opinions of emotions, (K9TV: Mutant Copper) he asked questions about some, such as fear (K9TV: Fear Itself) and love (K9TV: Aeolian). He even showed some, laughing when he saved the day, feeling fear (K9TV: Fear Itself) and being angry. (K9TV: Regeneration)

Features
K9 Mark I's mechanisms included rotating ear-probes, telescopic 'eye' probe, an extendable nose concealing a powerful laser weapon, flashing lights on the top and the 'eye' panel, waggling tail antennae, and ticker-tape tongue. His head could move up and down. His shell was painted in metallic gold/grey. Around K9's neck was a tartan collar, from which hung a silver disk. (DW: The Invisible Enemy) He was later modified to fly through the vacuum of space. (K9TV: Curse of Anubis)

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

When the Doctor left Sarah Jane Smith on Earth, he created K9 Mark III as Sarah's companion. The new mechanics of K9 Mark III included larger wheels and a front and back-wheel drive. K9 was also given a brand new coat of paint (this time a metallic blue) and a handle on top of his shell to make carrying him easier. (KAC: A Girl's Best Friend)

When the Tenth Doctor created K9 Mark IV to replace K9 Mark III, he added a shiny metallic blue paint job and other improvements, including an omniflexible hyperlink facility. (DW: School Reunion) Later, though, K9 reverted to his old dark green colour. (SJA: Invasion of the Bane) In battling Mr Smith (and following the battle) K9 displayed a teleport facility and a laser weapon similar to the previous K9s'. (SJA: The Lost Boy)

After K9 Mark I regenerated into K9 Mark 2, his design was radically altered. His ear probes were replaced with larger silver aerials. A set of blue lights on his head flashed when he spoke. Most of his body was dark silver and a silver dog bone was located under his neck. He seemed to have the same capabilities as Mark I but was presumably more advanced. (K9TV: Regeneration)

After K9 Mark 2's apparent rejuvenation, he looked similar to his predecessor, but with a bright blue coat of paint and K9 Mark I's old collar. (K9TV: The Eclipse of the Korven)

Marks

 * K9 Mark I was created about the year 5000 by Professor Marius, who gifted the dog to the Fourth Doctor and Leela. He was left behind with Leela on Gallifrey. (DW: The Invasion of Time) Some time later, he was blown up by a bomb on Gallifrey, (BFG: Imperiatrix) but survived. This model came to an end when Alistair Gryffen's Space-Time Manipulator randomly pulled him to London in the year 2050. There, he almost immediately self-destructed to protect Gryffen and a group of teenagers from Jixen warriors. (K9TV: Regeneration)
 * K9 Mark II was created by the Fourth Doctor as a "backup" when it became obvious that the Mark I was becoming erratic. (CC: The Time Vampire) He was left behind with Romana II in E-space, (DW: Warriors' Gate; BBV: The Choice, The Search) and apparently made it back to Gallifrey when she became Lady President of the High Council. (WEB: Shada, BFG: most titles)
 * K9 Mark III was a gift from the Doctor to Sarah Jane Smith (KAC: A Girl's Best Friend). He sacrificed himself to save Deffry Vale High School from Krillitanes. (DW: School Reunion)
 * K9 Mark IV was a recreation and enhancement of the Mark III created by the Tenth Doctor as a second present for Sarah Jane. (DW: School Reunion) This model continued in service to his mistress, Luke Smith, Clyde Langer, and Rani Chandra and was known by Maria Jackson and Kelsey Hooper.
 * K9 Mark 2 was the result of the activation of the Mark I's on-board regeneration unit. He had only very limited memories of his past as the Mark I. He had many adventures with Alistair Gryffen, Jorjie Turner, Darius Pike and his new master Starkey. (K9TV: Regeneration, The Bounty Hunter)
 * Orthrus was an attempt by Drake and the Department to replicate K9, but it was of vastly inferior design. (K9TV: Jaws of Orthrus)

Behind the scenes

 * In an interview, the writers said they originally wanted to name K9 "Pluto", after the Disney character; however, Disney refused permission.
 * The voice of K9 was inspired by the film, Billion Dollar Brain, albeit at a much high pitch.
 * K9 was also a contestant on the Doctor Who special of The Weakest Link. While the other contestants were Doctor Who actors appearing as themselves, K9 remained in-character and was the first contestant to be voted off.
 * K9 was referenced on the American tv show Community, as the character Abed describes himself as a dispassionate observer in the style of various other tv/movie characters.
 * K9 also appears in the non-canonical 1990 special Search Out Space. It is not known which model of K9 this is supposed to be.