Changes

===Third Doctor (1970-1974)===

===Third Doctor (1970-1974)===

[[Jon Pertwee]]'s Third Doctor was Earth-bound for much of his tenure, a move that was partly motivated by budgeting constraints in production. In the stories themselves, this was explained by the Doctor's race - the Time Lords - imposing an exile upon him due to alleged crimes prosecuted in ''The War Games''. During this time, the United Nations Intelligence Taskforce ("UNIT") was a key element of plots - the Doctor was officially UNIT's scientific advisor, but he frequently attempts to break free of the Time Lords' imposition of exile.

[[Jon Pertwee]]'s Third Doctor was Earth-bound for much of his tenure, a move that was partly motivated by budgeting constraints in production. In the stories themselves, this was explained by the Doctor's race - the Time Lords - imposing an exile upon him due to alleged crimes prosecuted in ''The War Games''. During this time, the United Nations Intelligence Taskforce ("UNIT") was a key element of plots - the Doctor was officially UNIT's scientific advisor, but he frequently attempts to break free of the Time Lords' imposition of exile.  The Third Doctor regenerated in ''Planet of the Spiders,'' after being exposed to large amounts of radiation.

===Fourth Doctor (1974-1981)===

===Fourth Doctor (1974-1981)===