As of 2017, season 8 remains notable for being the season with the most number of regular characters. Not only did it see a new companion in the form of Jo Grant, but it featured a regular enemy — The Master — who was the first regular Time Lord enemy of the Doctor to appear more than twice, and an expanded regular UNIT cast that now included Sergeant Benton and Mike Yates in most episodes. Adding in returning regulars Jon Pertwee and Nicholas Courtney, the regular cast swelled to six.
8 - 1Terror of the Autons (1) Jan. 02, 1971
8 - 2Terror of the Autons (2) Jan. 09, 1971
8 - 3Terror of the Autons (3) Jan. 16, 1971
8 - 4Terror of the Autons (4) Jan. 23, 1971
8 - 5The Mind of Evil (1) Jan. 30, 1971
8 - 6The Mind of Evil (2) Feb. 06, 1971
8 - 7The Mind of Evil (3) Feb. 13, 1971
8 - 8The Mind of Evil (4) Feb. 20, 1971
8 - 9The Mind of Evil (5) Feb. 27, 1971
8 - 10The Mind of Evil (6) Mar. 06, 1971
8 - 11The Claws of Axos (1) Mar. 13, 1971
8 - 12The Claws of Axos (2) Mar. 20, 1971
8 - 13The Claws of Axos (3) Mar. 27, 1971
8 - 14The Claws of Axos (4) Apr. 03, 1971
8 - 15Colony in Space (1) Apr. 10, 1971
8 - 16Colony in Space (2) Apr. 17, 1971
8 - 17Colony in Space (3) Apr. 24, 1971
8 - 18Colony in Space (4) May. 01, 1971
8 - 19Colony in Space (5) May. 08, 1971
8 - 20Colony in Space (6) May. 15, 1971
8 - 21The Dæmons (1) May. 22, 1971
8 - 22The Dæmons (2) May. 29, 1971
8 - 23The Dæmons (3) Jun. 05, 1971
8 - 24The Dæmons (4) Jun. 12, 1971
8 - 25The Dæmons (5) Jun. 19, 1971