Doctor's companion

In the long-running BBC television science fiction programme Doctor Who and related works, the term "companion" refers to a character who travels with, or shares the adventures of the Doctor. In most Doctor Who stories, the primary companion acts as an audience surrogate. They provide the lens through which the viewer is introduced to the series. The companion character often furthers the story by asking questions and getting into trouble, or by helping, rescuing, or challenging the Doctor. This designation is applied to a character by the show's producers and appears in the BBC's promotional material and off-screen fictional terminology. Until the modern revival of the series in 2005, the term was rarely used on-screen. The Doctor also refers to the show's other leads as his "friends" or "assistants"; the British press have also used the latter term.

In the earliest episodes of Doctor Who, the dramatic structure of the programme's cast was rather different from the hero-and-sidekick pattern that emerged later. Initially, the character of the Doctor was unclear, with uncertain motives and abilities. The protagonists were schoolteachers Ian Chesterton and Barbara Wright, who provided the audience's point of view in stories set in Earth's history and on alien worlds. Ian in particular served the role of the action hero. The fourth character was the Doctor's granddaughter, Susan, who (though initially presented as an "unearthly child") was intended as an identification figure for younger viewers.

Carole Ann Ford, who played Susan Foreman, became unhappy with the lack of development for her character and chose to leave in its second series. The character of Susan was married off to a freedom fighter and left behind to rebuild a Dalek-ravaged Earth. Doctor Who's producers replaced Susan with another young female character, Vicki. Similarly, when Ian and Barbara left, the "action hero" position was filled by astronaut Steven Taylor. This grouping of the Doctor, a young heroic male, and an attractive young female became the programme's pattern throughout the 1960s.

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