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Characters / Doctor Who K9

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K9 Mark ISpelling  (Fourth and Tenth Doctor)
First appearance: "The Invisible Enemy" (1977)
Voiced by: John Leeson (1977–78, 2009)

"Affirmative master!"

The first robot-buddy of the franchise, hailing from the 51st century. K-9 Mark I, the original built by Professor Marius, was a highly advanced robot built to resemble a dog. Known for his laser nose, propensity to speak in Literal-Minded terms, and his constant uttering of "Affirmative", or "Negative", which stuck with his descendants. He had a short run and remained with Leela on Gallifrey. This was because his prop's maintenance sucked. Prone to break even if it hit a simple bump on the floor, he was quickly replaced by Mark II. Mark I was later brought back in his own series but due to design copyrights, he got destroyed in a fight with the Jixen and regenerated through a special repair unit into a brand new appearance with Laser-Guided Amnesia to sever all explicit ties with the Doctor Who franchise.


Tropes associated with the television continuity

Doctor Who

  • Badass Adorable
  • Breakout Character: Like Sarah Jane, he got two spin-off television series, even if they were shortlived.
  • The Cameo: The original K-9 hosted the 40th anniversary celebrations for the series while it was in its so-called wilderness years, voiced by John Leeson.
    • The newly-introduced Mark IV, also played by Leeson, appeared on The Weakest Link in 2007 for a promotion of Series 2, but he was mostly a Joke Character who was voted off immediately. The reason was that the prop operators feared K-9's dreaded habit of breaking down at the most inconvenient times would happen during the game, so they made sure he would be voted off in the first round (the game's selection of DW cast itself admittedly agreed to rig their votes so that only members of the regular cast at the time were guaranteed to stay on till the final round and guest cast got the boot—but this didn't stop top-billed actors from being voted off).
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    • Also cameoed on Queer as Folk as the perfect gift for Doctor Who fan Vince, an Author Avatar in this respect of Who fan and future New-Who re-creator and showrunner Russell T. Davies.
  • Canine Companion: The Doctor insisted on treating him like an actual dog.
  • Catchphrase: "Affirmative." "Negative." "Master/Mistress?"
  • Cute Machines: He is very adorable.
  • Deadpan Snarker: He got into many a snarking match with Four.
  • Do-Anything Robot: Laser beam, hacking computers, defensive protocols, beating the Doctor at Chess, being a Deus ex Machina...
  • Family Friendly Firearm: K-9's ever-convenient laser beam has a kill option, but is always set on stun.
  • Hypercompetent Sidekick: Particularly if viewed specifically as The Doctor's sidekick.
  • Insufferable Genius: He's a futuristic alien super computer, so he's just as smart as the Doctor. And he's well aware of it.
    The Doctor: We all make mistakes sometimes, don't we, K9?
    K9: Negative.
  • Kid-Appeal Character: K-9 was a huge hit with children.
  • Made of Iron: Subverted, K9 gets damaged often despite his claims of not being made of tin.
  • Non-Human Sidekick: Serves as a beeping Robot Buddy for The Doctor in the original series.
  • Only Sane Man: K9 seems to cater to this.
  • Pint-Sized Powerhouse: His laser weapon helps him take care of opponents often twice his size.
  • Punny Name: Get it? K-9? Because it looks like a dog! K-9! As in CA-NINE.
  • Robot Buddy: To the Doctor, Romana, Leela and Sarah Jane.
  • Robot Dog: A medical robot, originally.
  • The Spock
  • Smart People Play Chess
  • Think Nothing of It: Used a few times.
  • Zeerust: Lampshaded in "School Reunion".
    Rose: It looks so... disco.
    Tenth Doctor: Oi! In the year 5000 this was cutting-edge!


Tropes associated with Big Finish

Voiced by: John Leeson

  • No Social Skills: He's basically a talking calculator on wheels and the one thing going for K-9 is that everyone thinks he's cute.
  • Not Now, Kiddo: A running gag with the Fourth Doctor, who'd tell K-9 to be quiet just before k-9 has something important to tell him.
  • One Steve Limit: Discussed with the Doctor, when he gets very confused as to why K-9 refers to both The Doctor and The Master as "Master". He tells K-9 to call The Master "The Renegade".
  • Only Sane Man: Likes to think of himself as this, but his complete lack of understanding humans leads to very awkward (and funny) situations, and averts this trope.
  • Sliding Scale of Robot Intelligence: Frequently displays Level 4 abilities in episodes like "Requiem for the Rocket Men", where he's able to do dozens of mathematical equations simultaneously in his head while assisting the Doctor in about three other difficult tasks.

K9 Mark II

First appearance: "The Ribos Operation" (1978)
Voiced by: John Leeson (1978, 1980–81, 1990, 1993); David Brierley (1979–80); Roy Skelton (1979)

K-9 Mark II was the replacement for Mark I, who would now only stun, not kill things (at least not living things - he does kill at least one robot). Affectionately referring to the Doctor as "Master", Mark II was conceived because K-9 was popular with the kids, but the prop needed a redesign after breaking down all the time. He stayed with Romana II when she stopped travelling in the TARDIS. At one point, John Leeson quit signing on to voice the character and David Brierley was brought on as his interim voice actor. He tried to imitate Leeson's portrayal, but still had a noticeably different inflection, so the voice change was Hand Waved as K-9 contracting robot laryngitis, so it pained him to speak and he had a hoarser voice when he did. This let writers coast by with K-9 having as few lines as necessary to somewhat mask Brierley's portrayal until Leeson finally agreed to resume his duty as K-9's definitive voice actor.

Tropes associated with the television continuity

  • Literal-Minded: More so than the Mark I.
    Romana: Uh, K-9, what is tennis?
    K9: Real, lawn or table, mistress?
    Romana: Never mind. Forget it.
    K9: Forget. Erase memory banks concerning tennis. [whirring sound] Memory erased.

Tropes associated with Big Finish

Voiced by: John Leeson

K-9 travels with the Doctor, and Romana, but has on occasion been relegated to looking after the TARDIS while his Time Lord friends go out exploring. He eventually joins back up with Leela and Romana in the Big Finish spinoff Gallifrey. On one occasion, both K-9 and Romana, after establishing themselves on Gallifrey, rejoin with the Doctor for a once-off adventure involving Professor Chronotis.

K9 Mark III

First appearance: "Doctor Who Annual 1982: Inter-Galactic Cat" (1981)
Voiced by: John Leeson (1981, 1983, 2006)

K-9 Mark III was the model who got given to Sarah Jane Smith as a gift from the Doctor, in the One-Episode Wonder K-9 and Company. He turned up in a few comic stories and "The Five Doctors", and that was it (unless you count the non-canon "Search Out Space" and "Dimensions in Time"). He didn't appear again until 2006 in a few audio stories leading up to Sarah Jane Smith's return to the series proper, where he got badly damaged, fell into disrepair, and rusted in Sarah Jane's attic because she didn't know how to fix a robot dog with futuristic technology, nor could she reveal said technology to anyone before its time. Mark III's functionality was somewhat restored by the Tenth Doctor, long enough for him to give his life by defeating the Krillitanes.

Tropes associated with the television continuity

K9 & Company

Doctor Who

  • Awesomeness by Analysis: The Tenth Doctor and Sarah-Jane repair him so he can figure out what's on with the chips at a school they're investigating. Once he's fixed up, he works it out quickly.
  • The Cameo: Briefly appears during "The Five Doctors", when we see Sarah-Jane leaving for work.
  • Famous Last Words: "You bad dog!" "Affirmative."
  • Heroic Sacrifice: Blows up a bunch of Krillitane oil tanks, but in order to do so has to be right by the barrels.
  • Took a Level in Badass: Thanks to an improved special effects budget, K9 gets to zap multiple Krillitane when he reappears in "School Reunion".

K9 Mark IV

First appearance: "School Reunion" (2006)
Voiced by: John Leeson (2006, 2007, 2008, 2009-2010)

K-9 Mark IV was given to Sarah Jane by the Tenth Doctor as a replacement for Mark III, along with a sonic lipstick inside his casing. Mark IV was better associated as Sarah Jane's K-9 than the Doctor's, and this loyal robot called her "Mistress". He sported a more computerized-sounding voice and did not have as many locomotion woes because he could hover up stairs. He served as Sarah Jane's loyal pet and had an ongoing rivalry with Mr. Smith, the Xylok supercomputer. However, licensing issues left him trying to close a black hole after a Switzerland experiment went awry for the first three seasons of the The Sarah Jane Adventures. Then, he had a more active role in the plot, until the Australian K-9 series came out and the licensing disputes resurfaced, causing him to go to college with Luke Smith and return to light roles in the show.

Tropes associated with the television continuity

Doctor Who

  • Big Damn Heroes: During "Journey's End", since the Doctor has forgotten the TARDIS base code, Sarah-Jane calls K9 out to provide it.
  • The Nth Doctor: While physically distinct, he's treated as being the same individual as Mark III

The Sarah Jane Adventures

  • Big Damn Heroes: His cameo appearances prior to joining the regular cast mostly consisted of him teleporting in when Sarah calls for him to save the day.
  • Put on a Bus: Leaves to accompany Luke to university. (Out-of-universe, written out due to rights issues following the beginning of the Australian K-9 TV show.)
  • Robot Dog: He's a robotic dog from the future, a gift from the Doctor.
  • Sesquipedalian Loquaciousness: Lampshaded on several occasions.
    K-9 *In reference to Mr Smith*: Contact with that computer interferes with this unit's synaptic circuits.
    Clyde: You mean he gets on your nerves.
    K-9(More assertively that normal): Affirmative.
  • Spock Speak: "Affirmative Mistress".

K9 Mark 2

First appearance: "Regeneration" (2009)
Voiced by: John Leeson (2009-2010)

Tropes associated with the television continuity

  • The Nth Doctor: Largely subverted in that, while each K-9 unit is essentially the exact same thing as the previous model, the version in the K-9 spinoff looks and acts drastically different.

Example of: