K-9

What is K9?

K9 — occasionally written as K-9 or K•9 — was the designation given to a series of intelligent, dog-like robots who served as companions of Professor Marius, the Fourth Doctor, Leela, Romana, Sarah Jane Smith, Luke Smith, and Starkey. They were programmed to be both loyal and logical, with a habit of taking orders literally, sometimes to the dismay of the Doctor or his companion.

K9 first appeared in the 1977 Doctor Who story The Invisible Enemy. K9 was created by Professor Marius in the year 5000. The Doctor and his companion Leela helped Professor Marius defeat an alien virus. After the virus was defeated the professor asked if the Doctor to keep K9 and look after him. After many adventures with the Doctor, K9 Mark I stayed behind on Gallifrey to look after Leela.

Since then, various versions of K9 were built by the Doctor to be companions. Mark II was given the Time Lady Romana. Mark III was given to one of the most beloved Doctor Who companions of all time, Sarah-Jane Smith and appeared in the "Sarah Jane Adventures" and new series Doctor Who episode, "School Reunion" where he sacrificed himself to save the Doctor and his companions. The Doctor then built K9 Mark IV for Sara-Jane as her new companion.