One of the many unofficial spin off series from the BBC TV show "Doctor who", created using a contract loophole which allowed production companies to license characters directly from their creators.
An attempt to produce a K-9 spin-off series was already made in 1981 with the pilot K-9 and Company (1981), starring Elisabeth Sladen (Sarah Jane Smith) and John Leeson (K-9). Initially greenlit by BBC One controller Bill Cotton, the show was later scrapped by new controller Alan Hart, who disliked the idea of it.
John Leeson returned to provide the voice of K9.
The first 3 note intervals of the main melody of the K9 titles theme is a direct nod to the original Dr Who theme by Ron Grainer and the extraordinary Delia Derbyshire .
(5th octave up to minor 6th then 5th.)
The version of K9 in this show is K9 Mark I, the very same one which The 4th Doctor left with Leela on Gallifrey in the original Doctor Who series.