K9 Mark I, II, III, and IV addressed whoever was directing them as "Master" or "Mistress" depending upon gender, and used the formal "affirmative" and "negative" rather than "yes" and "no". They were programmed to be both loyal and logical, with a penchant for taking orders literally, almost to a fault. Their striped collars mirrored the Fourth Doctor's trademark scarf.
The Virgin New Adventures seventh Doctor novel Lungbarrow (written by former Doctor TV series writer Marc Platt) featured K9s Marks I and II meeting for the first time on Gallifrey during the events surrounding the disappearance of the Doctor's entire family house and his living relatives, which also featured many previous established Gallifreyan based characters. The two collaborated towards rescuing the Doctor, then current companion Chris Cwej and the Doctor's lost family. This novel also served as the direct lead-in story to the 1996 Doctor Who telemovie.
Solid K9 Training, founded by award-winning, internationally-acclaimed dog trainer Jeff Gellman, is one of the nations most effective and respected dog training services providing no-nonsense, "Real World" training methods throughout New England. Serving dog owners from Hartford, CT to Boston, MA in our multifaceted, secure and 24/7 staffed Solid K9 Training Center in Providence, RI, as well as all throughout the nation with Jeff's wildly successful RV Dog Trainer Tour. We will train any dog, regardless of breed, shape, size or history. We work to fix all dog behavior issues including excessive barking, growling, snapping, nipping, dog aggression (fighting), human aggression (biting), child aggression, pulling on leash, leash aggression, leash reactivity, skateboard reactivity, resource guarding, jumping on people, fear issues, anxiety issues, separation anxiety, chewing and destroying household items, running away, not listening, door bolting, stealing food, getting into the trash, cat aggression, chasing game, and killing animals/game. We also have a renowned reputation specializing in obedience training, which includes heeling and walking properly on a leash, sit/stay, down/stay, place, recall training (come to owner), and crate training. Our Training services include Board and Train behavioral modification, 1 on 1 Training, Obedience Classes, Puppy Training programs, Boarding / Board & Play, Daycare, and many free dog training resources including Dog training advice videos, dog training webinars, and Dog Training Q and A videos on Periscope on Monday and Wednesday nights. Our behavior modification training is cutting edge, using techniques like modern low level E-collar (remote collar) training and food and clicker training. Solid K9 Training has a worldwide reputation of being able to handle the most challenging dog behaviors and often times other dog trainers will refer their more serious cases to us. For more information on our services offered, as well as free dog training tutorial videos, please see my website and other social media pages:
Jealous, Possessive by Paul Magrs, the "Scorpio" story in Big Finish's anthology Short Trips: Zodiac features K9 Mark I and Mark II relaying their exploits to each other, and their veiled put-downs to each other reveal that each considers the other to be the "inferior" version. This attitude is also occasionally hinted at in the way the two units refer to each other in the Gallifrey audio series.
Having left K9 Mark III to Sarah Jane (TV: A Girl's Best Friend) following their travels with Adric in his fourth incarnation, (PROSE: Just a Small Problem) the Doctor eventually built K9 Mark IV. The Eighth Doctor mentioned Mark IV when he met Sarah Jane in 1996. He indicated that the effort in constructing Mark III was "nothing" in comparison to Mark IV. (PROSE: Interference - Book Two)
In 1985, a series of gamebooks featuring the Sixth Doctor were published by Severn House under the title Make your own adventure with Doctor Who in Britain and Find Your Fate — Doctor Who in the United States. These books were actually written by scriptwriters for the television series. Martin wrote Search for the Doctor which takes place in the mid-21st century and features K9 Mark IV being reunited with the Sixth Doctor long after Sarah's death.
Although John Leeson has been the primary voice actor for K9 since his introduction, two other actors have voiced the character. David Brierley voiced K9 during Season 17 after Leeson chose not to return to the series (Leeson subsequently signed up again for Season 18), and Roy Skelton, better known for his work voicing Daleks, voiced the character in Destiny of the Daleks when all was required of K9 was a croaking sound due to the character contracting a form of robot laryngitis.