I did forget to mention in my review of "The Brain of Morbius" that there is a little bit of trivia/controversy surrounding the episode.
At one point the Doctor and Morbius engage in a duel of minds -- each trying to mentally force the other back along his respective timeline. This is given representation by a visual display of images of each Time Lord's past selves. Morbius, apparently winning, pushes the Doctor past his "first" incarnation to images of another several men.
Hinchcliffe made it clear that he always intended this to mean that the First Doctor was NOT the "first" Doctor but fans later pointed out that the anniversary story "The Three Doctors" established that that First Doctor was indeed the Doctor's first incarnation. The bit of trivia comes from the fact that Hinchcliffe had also wanted to photograph recognizable actors for incarnations but was unable to complete the feat and so instead wrangled members of the crew of this story and the one following in production -- "Seeds of Doom" -- to appear in period dress. As a result the "other Doctors" and Morbius's who appear in the sequence are:
Philip Hinchcliffe himself, Robert Holmes, Christopher Barry the episode's director, Douglas Camfield who was going to be directing "Seeds of Doom", George Gallacio the production manager, Robert Banks Stewart writer of "Seeds of Doom", and production assistants Chris Baker and Graeme Harper.