Born July 7, 1919 in London, England. Died May 20, 1996.
He was basically a comedian. His schoolastic career seemed to consist of entering a school and shortly afterward being expelled. After giving up on school, he became an actor and a very successful one. The roles he had were on the lighter side, but they included stage, radio, movies, and finally TV. Jon was The Doctor for five years, surpassing Hartnell and Troughton and up until the current time only surpassed by Tom Baker. Jon eventually decided to leave for the same reason Patrick Troughton gave, worries about type-casting. His post-Who career continued to be successful, and he still came to the Dr Who conventions.
Every new Doctor has to incorporate the Doctors that came before, after all, he's them, but he also has to add something new of his own. Something the third Doctor liked was dressing up, and even though one of his two previous selves called him "Fancy Pants" and the other called him a Dandy, dressing up became a part of all the future Doctors. For a lot of them, the first thing they did after a regeneration was to go into the TARDIS closet (which must be larger than some solar systems) and pick out a new outfit. Pertwee also incorporated a sense of fun into his Doctor that also leaked over into some future Doctors. Zooming around in his little yellow Model-T could even be better than running.