K9 Mark II


 * Not to be confused with K9 Mark 2, an ally of Starkey.

K9 Mark II was the second K9 based on a robot originally built by Professor Marius, though constructed by the Doctor.

Biography
Mark II was constructed as a replacement for the Doctor after Mark I, decided to stay on Gallifrey with Leela. The Doctor appeared to have prepared for the possibility of losing Mark I, as he already had Mark II (or at least its components) prepared and in storage. (DW: The Invasion of Time)

Quest for the Key to Time
This version of K9 accompanied the Doctor and Romana on their quest to locate the segments of the Key to Time. The Doctor began using a Dog whistle to alert K9 or to summon him. (DW: The Ribos Operation)

On Tara, K9 was able to quickly disable several guards in the employ of Cound Grendel of Gracht. He traveled in a boat with the Doctor in a passage under the count's castle cutting a way through with his blaster. The Doctor left K9 in the boat as he went to foil the count's plot. (DW: The Androids of Tara)

When the TARDIS landed on Delta III the swampy terrain made it impossible for K9 to accompany the Doctor and Romana and so he remained in the TARDIS. (DW: The Power of Kroll)

While searching for the sixth segment they landed on the planet Atrios. K9 was tricked into entering a furnace for the recycling of metal, the Doctor was able to rescue him before he was melted. He transmatted to the planet Zeos where he met the supercomputer Mentalis, he had a conversation with him and declared that it was good to talk with someone who was not as illogical or unpredictable as a flesh and blood being. K9 again transmatted, arriving on the Planet of Evil. He was turned by The Shadow to do his bidding, however the Doctor was able to remove the control matrix implanted by the Shadow restoring him to his former self. (DW: The Armageddon Factor)

Further adventures
The Doctor was a making repairs to K9's brain circuit when he found that K9 had contracted laryngitis and had lost his voice as a result. K9 was left in the TARDIS while the Doctor and Romana battled the Daleks and Davros. (DW: Destiny of the Daleks) Later he 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)

In E-space, K9 led the attack on the castle of the Three Who Rule. He shot many of the guards, doing most of the work. The Doctor made Ivo apologise to K9 for doubting him. (DW: State of Decay)

Damaged by the time winds, K9 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) The Doctor, meanwhile, chose not to replace K9 again, though he did build/obtain a Mark III that he gifted to Sarah Jane Smith (KAC: A Girl's Best Friend) and apparently at one point also created a Mark IV that was also gifted to Smith upon the destruction of Mark III. (DW: School Reunion)

As for Mark II, he was later repaired, and accompanied Romana when she returned to N-Space. During Romana's term as President of Gallifrey, K9 Mark II served as her aide and advisor. (NA: Lungbarrow) He may have also shared an adventure with Romana and later incarnation of the Doctor at some point after this (WC: Shada)

What ultimately became of K9 Mark II is unknown, as he is no longer present during events before and after the arrival of Pandora (BFG: Gallifrey) or the events of The War which resulted in Romana regenerating into a third incarnation (EDA: The Shadows of Avalon).

Personality
K9 was faithful to the Doctor, titling him as master. He corrected him when necessary. (DW: The Ribos Operation) He was happy to have a conversation with the supercomputer Mentalis, declaring it better than talking to unpredictable life forms. (DW: The Armageddon Factor) He declared that he didn’t feel anything nor found it necessary to do so. (DW: Warriors' Gate)

K9 had no problem with killing those who posed a threat such as Count Grendal's men or the guards of the Three Who Rule. (DW: The Androids of Tara, State of Decay)

Features
After K9 Mark I was left behind with Leela on Gallifrey, The Doctor built an improved K9 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 K9 now 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 that of the TARDIS. (DW: The Invasion of Time)

Production notes

 * The production team used the same prop for Mark II as they had for K9 Mark I.
 * In WC: Shada, K9 mentions that Earth's soil interfered with his traction (a joke on the original prop's difficulty travelling in a straight line).

Casting
While John Leeson provided K9 Mark II's stories in all his other appearances, another actor, David Brierley voiced him in The Creature from the Pit, Nightmare of Eden and The Horns of Nimon. Leeson took over the role again from The Leisure Hive onward.