...That's when I found the first reference to the Six Doctors working title and - foolishly - assumed it was just a typo).
Have pity on an American Whovian and tell me...
Once C. Baker was on board, had they planned to do it AGAIN?
No it is to do with Robert Holmes's original story which had the First Doctor being replaced by a robot duplicate.
And in keeping with the tradition of robot duplicates of the 1st Doctor, this one was distinguishable because he:
1. Actually remembered his lines.
2. Moved his lips completely independently of any words coming out.
3. Didn't look a thing like the Doctor!!!!!