Portrayed by: John Leeson, David Brierly
Tenure: 18 stories, from The Invisible Enemy (Oct, 1977) to Warriors’ Gate (Jan, 1981), plus “School Reunion” (April, 2006)
Background: There have been several versions of K-9 (Mark I, Mark II, Mark III, Mark IV, as well as another version on K9, an Australian spinoff series). When Leela decided to stay behind on Gallifrey rather than continue traveling with the Doctor, Mark I stayed with her. Mark II stayed with Romana when she left the TARDIS to stay in E-Space rather than return to N-Space and become President of the Time Lords. The Doctor sent Mark III to Sarah Jane, care of her aunt, and it’s this version we meet in “School Reunion”. After K-9 Mark III sacrifices himself to allow the Doctor, Sarah Jane, Rose, and Mickey to escape, the Doctor leaves K-9 Mark IV with Sarah Jane when he leaves in the TARDIS.
Family/Friends: K-9 is introduced in The Invisible Enemy as the pet of Prof. Marius, who asks the Doctor if he’d like him when Marius is unable to keep him upon returning home to Earth. He is devoted to the Doctor, Leela, Romana, and Sarah Jane.
Personality: K-9 is intelligent, dryly humorous, and incredibly literal. He frequently plays the Doctor at chess, usually winning, and despite his monotone voice, often demonstrates a wide range of emotions. He is formal, saying “affirmative” or “negative” rather than yes or no, is very detail oriented, and is very focused on whatever task is given him by his Master or Mistress.
Special Skills: K-9 is a super-intelligent robot dog, so he has a great deal of computing power, substantial data banks (handy for exposition-dumping), and the ability to analyze materials. He can also shoot laser beams from his nose
Best Stories: The Sunmakers features a lot of K-9, who saves the day several times by blasting enemies or getting the group out of locked rooms. He’s similarly helpful in Nightmare of Eden, analyzing the drug and saving the Doctor and Romana several times, and he’s great in “School Reunion”, saving the day and prompting character development in Mickey.
Worst Stories: K-9 has a lot to do in the Armageddon Factor, but it’s a pretty dire story. He’s also in notorious stinkers The Creature from the Pit, The Horns of Nimon, and The Leisure Hive. There are also several stories where K-9 appears for only a few minutes, due to production issues, making his absence through the rest of the story particularly noticeable.
Highlights of tenure: Hunting down the Captain’s robot parrot in The Pirate Planet, keeping the Doctor’s ego in check (particularly with chess), and having perfect deadpan comedy timing
Lowlights of tenure: K-9 proved difficult much of the time, given his physical limitations as a prop. This led to the character having to be written out for long stretches of stories and his inability to move or speak explained, often rather clumsily.
“Optimism: belief that everything will work out well. Irrational, bordering on insane.” The Armageddon Factor
K-9: “The accuracy of this unit has deteriorated below zero utility.”
Adric: “You mean you’re worse than useless.”
K-9: “Affirmative.” Warriors’ Gate
“We are in a car.” “School Reunion”
Other notes: Producers considered writing out K-9 when Leela left, given the production hassles it was creating, but they decided to keep the character around due to his popularity with young viewers.