The role of the companion is a vital one. These characters are present either to attract viewers - as in the kilted Jamie or leather-clad Leela - or to provide a viewpoint with which the viewers can relate. In the original TARDIS crew, Ian and Barbara represented the average adult viewer by posing questions to the Doctor and needing to have things explained to them. Teenagers, meanwhile, related to Susan.
Over the years, things changed little. The need for companions that viewers could identify with diminished, but the need for characters that demanded explanations did not. Thus, companions became both a ready reason for describing the plot and, sometimes, a way to establish a secondary plotline.
It has been stated that there are three requirements for being a companion - one must be able to scream well, run down endless corridors, and convincingly ask "What is it, Doctor?" Although there have been several exceptions to the screaming rule, the other two generally hold true. Another, usually unspoken, rule seems to be that a companion must have a penchant for getting into trouble, therefore furthering the plot.
Despite the similarities, no two companions are exactly alike. Each has their own strengths and weaknesses. Some are traditional screamers, others are unconventional mold-breakers. Some are sweet and inoffensive, others are brash or vicious. Why, even a few are male! Browse through the list of the Doctor's fellow travellers, and discover just what it is that makes the role of the companion so vital and irresistible.
Susan
Carole Ann Ford
Ian Chesterton
William Russell
Barbara Wright
Jacqueline Hill
Vicki
Maureen O'Brien
Steven Taylor
Peter Purves
Katarina
Adrienne Hill
Sara Kingdom
Jean Marsh
Dorothea "Dodo" Chaplet
Jackie Lane
Ben Jackson
Michael Craze
Polly Wright
Anneke Wills
James Robert "Jamie" McCrimmon
Frazer Hines
Victoria Waterfield
Deborah Watling
Zoe Heriot
Wendy Padbury
Elizabeth "Liz" Shaw
Caroline John
Josephine "Jo" Grant
Katy Manning
Sarah Jane Smith
Elisabeth Sladen
Harry Sullivan
Ian Marter
Leela
Louise Jameson
K-9
voiced by John Leeson and David Brierley
the first Romanadvoratrelundar
Mary Tamm
the second Romanadvoratrelundar
Lalla Ward
Adric
Matthew Waterhouse
Nyssa
Sarah Sutton
Tegan Jovanka
Janet Fielding
Vislor Turlough
Mark Strickson
Kamelion
voiced by Gerald Flood
Perpugilliam "Peri" Brown
Nicola Bryant
Melanie "Mel" Bush
Bonnie Langford
Ace
Sophie Aldred
Grace Holloway
Daphne Ashbrook
Rose Tyler
Billie Piper
Adam Mitchell
Bruno Langley
Jack Harkness
John Barrowman
Mickey Smith
Noel Clarke