The second Doctor (Patrick Troughton's) first story was The Power of the Daleks, a six-part story broadcast between November and December of 1966, which sadly no longer exists except in audio format. The War Games were his last film in June 1969. He also returned to the role no less than three times, in The Three Doctors (December 1972 and January 1973), The Five Doctors (November 1983), and The Two Doctors (February and March 1985). But sadly Patrick Troughton passed away in 1987.
The Doctor had his very first regeneration in the story The Tenth Planet, after this most surprising occurrence took place the Doctor became younger with an entirely new personality. This Doctor displayed considerable knowledge and expertise gained through extensive travels, and had even gained some small measure of control over the TARDIS, although not much more than his predecessor. Patrick Troughton and Tom Baker shared some similar traits in personality on Doctor Who, they both acted quite childish sometimes and they both added a bit of humor into the show.
The second Doctor's last regular story was The War Games, broadcast in 1969. It was this ten-part story that revealed the Doctor's origins, which heretofore had only been hinted at: he was one of a race called the Timelords, who had mastery over time and space, but who were content to watch without interfering. The Doctor was taken back to his home world of Gallifrey, and put on trial for the crime of stealing a TARDIS and interfering in the universe outside. As a result, he was forced to regenerate, and put into exile on Earth in the twentieth century, with the knowledge of how to operate the TARDIS blocked from his mind.
Audio theme for the second Doctor (size: 287 KB. run time: 26.71 seconds).
Patrick Toughton (The second doctor) starred in the following Episodes: