|Mary Sue Brown|
|Planet of Origin:||Earth|
|Original era:||20th Century|
|First Appearance:||The Space Viking|
|Last Appearance:||The Last Minutes|
|Portrayed By:||Susannah York|
Initially introduced to the programme as a feminist photojournalist, she begins travelling with the Inspector after being abducted by his BOOTH. She continued to stay on with the him after he underwent metamorphosis and was assigned to 20th century Earth. During their adventures, she met the Blorgons, Rostraans, Circuit-Chaps, Sulphur Soldiers and Asterozoids.
Mary Sue chose to leave the Inspector in the serial "The Foot of Terror" after he was forced back to Kayaclasch, but not without arguing with him about being overly sensitive towards her human nature. Although never explicitly stated, it is heavily implied that the Inspector had feelings for Mary Sue when she travelled with him as an Associate.
In the revived series, both Mary Sue and FE-Line were reunited with the Tenth Inspector in the Series Two episode "The Embarrassing 15th Anniversary Reunion" while he was investigating happenings at a local nursery school during Picture Day, in which Mary Sue was the photographer. This caused some conflict between herself and Lily, which remains unresolved to this day. She also reappeared in the Series Four episodes "Return to Earth" and "Odyssey's Beginning" and at the end of the 2009 Christmas Special "The Last Minutes" in a non-speaking role.
Given her role as the Fourth Inspector's associate and that Inspector's rating as the Most Popular Inspector by the public, she has consistently been rated Most Popular Associate, though Lily Taylor and Constable Reggie Wigglesworth have taken over that spot in recent years.
Ms. York's effervescent manner made her extremely popular with fans, who found her independent spirit especially inspiring. Although she was diagnosed with cancer late in 2010, she refused chemotherapy and filmed three final episodes of the Predicaments.
The Inspector is the only one Mary Sue does not permit to call merely by her first name, Mary. When Nitya corrects him on this, the Inspector states that "She likes it when I call her Mary Sue."