The twenty-first season of British science fiction television series "Doctor Who" began on 5 January 1984 with the 5th Doctor (Peter Davison) serial "Warriors of the Deep", and ended with Colin Baker's first serial "The Twin Dilemma". For only the second time (the first being during season 4), the entire TARDIS crew changed over the course of a single season.
The twenty-first season the entire TARDIS crew was the only time the curse of the crew changed over a single season.
This was the second time (the first being during season 4), the entire TARDIS crew changed over the course of a single season.