I'm slowly running out of Old Who. I've got 116 episodes left. One season left of Hartnell, one season of Troughton, most all of Davidson's tenure, 2 serials of Colin Baker, and 3 serials of Sylvester McCoy.
I'm currently going into Harnell's third season, his second season was a surprisingly good pickup from his previous season. I really enjoyed Planet of the Giants, The Rescue, The Romans, and The Webbed Planet. Time Meddler was also very good.
Kind of sad to see Susan, Barbara, and Ian all leave the Tardis during the second season.
Some things I have noted from Hartnell's era. Terry Nation is probably the most influential writer in Doctor Who, followed by Dennis Spooner. Spooner added comedy to the series, as well as the Time Meddler, worked with Terry Nation, and was given the first serial of Troughton's era to help define his character before Spooner left the show for good.
I also think that Susan leaving the show had the most profound effect on the show than anything else. Carole Ann Ford left because neither she nor Hartnell could convince the writers/producers to give Susan character growth. I found something from William Russell, Ian, that talked about her leaving the show and that it created a hole in the cast. Later he and Barbara, Jacqueline Hill, left, though I'm not entirely sure why.
For most shows, having an almost entire cast change out would be devastating, even today. Good news was the Doctor was the most popular character so that the show was not lost on the viewers. Vicky also made a good replacement for Susan. After many more replacements for the sidekicks, the writers decided they wanted to replace Hartnell in the Celestial Toymaker episode. The serial starts off with the Doctor being made invisible, but when he becomes visible at the end, his actor was supposed to have been replaced. The higher ups decided to veto that, but then allowed it only a few short serials later in Tenth Planet. An entire cast change from when the show initially began. XD Amazing.
Si-Fy and Fantasy, that is where my heart lies. To Doctor Who and its 18 years of brilliance, still waiting on the 50 yr anniversary!