Marius

From TARDIS Index File, the free Doctor Who reference.

Marius
Also known as:
Race:	Human
Home Planet:	Earth
Home Era:	5000
Appearances:	DW: The Invisible Enemy
Actor:	Frederick Jaeger

Professor Marius was a scientist who worked at the Bi-Al Foundation in the year 5000 as a specialist in extraterrestrial pathological endomorphisms. While on Earth he also wanted a dog so he constructed K-9 to accompany and assist him in his work. He helped the Doctor defeat the Swarm, although he himself was briefly infected by it and so freed the nucleus and made it grow in size. Afterwards, Marius gave K-9 to the Doctor to take with him on his journeys. (DW: The Invisible Enemy)