When Doctor Who was relaunched in 2005 at the hands of Russell T. Davies, it was returning after nearly a decade away from the public eye. Russell T. Davies viewed the relaunch as more of a picking up where the story left off as opposed to being a complete restart as the current trend for bringing new life to past entertainment properties.
To aid new viewers in getting up to speed with the lore of Doctor Who, a new companion, Rose Tyler, played by Billie Piper, so the getting to know the world of Doctor Who is told through the eyes of a character that’s meant to be the audience, someone from our time and experience being drawn into this fantastic world for an incredible journey. Old enemies of the Doctor, familiar to long time fans are new to Rose and new audience members and they become educated quickly. The end of the first season taught the audience about one of the Doctor’s greatest tricks to ensure it’s long term endurance, the ability of the Doctor to regenerate.
As Christopher Eccleston left the series and David Tennant took over the role, for the character of the Doctor, what this allows is the Doctor to take on a new face and personality every time the Doctor regenerates. This easy way to change actors also allows each new actor to bring their own touch to an established character. David Tennant’s first season as the tenth Doctor was aided by Billie Piper’s second season as Rose Tyler, as those of us new to Doctor Who had Rose’s getting used to the new Doctor to help aid us through the process as well. Eventually the storyline had Rose depart being the Doctor’s companion and we had a few others take on being the Doctor’s companion during David Tennant’s run.