 Since 1963 , the Doctor has travelled with various companions who generally serve to remind him of his " moral duty " . The casting of Billie Piper as the Ninth Doctor 's primary female companion Rose Tyler was announced in May 2004 . Julie Gardner felt that the young actress and former pop star was perfect as a " unique " and " dynamic " companion for the Doctor . Press for the series focused heavily on the fact that Rose was to be more independent and courageous than previous companions . Prior to the casting of Piper , Eccleston had joked that " I 'll be doing the running around screaming . " He later opined that Rose is not as " vulnerable " as previous companions and that " she 's as brave and courageous and intelligent as he is " citing the fact that she saves the Doctor 's life . Piper remarked that the Doctor challenges Rose more than anyone else in her life and that he in turn sees in her " she has huge potential , to be someone really , really great . " Eccleston felt that Rose is a " heroine " who " teaches [ the Doctor ] huge emotional lessons " . He felt that the relationship between the two characters was " love at first sight " although in a more mysterious fashion than a conventional love affair . Commentators on the series noted the romantic tension between the two characters . In their book Who is the Doctor ? , Graeme Burk and Robert Smith described the climactic kiss between the Ninth Doctor and Rose in " The Parting of the Ways " as being something " we all secretly wanted , even though it ultimately killed him " . 
