Dot Cotton

Dot Cotton was a fictional character who appeared in the British soap opera EastEnders. Clara Oswald described her as a "famous Cockney chimney".

During the Twelfth Doctor's imprisonment in the Prison, Clara took one of Class 2A's art lessons. She asked the students to paint a placard with the phrase "SAVE THE DOCTOR", but instead they got confused and began to paint "SAVE DOT COTTON". (PROSE: The Blood Cell)

Information from invalid sources
While the Eleventh Doctor was trying to drop off Dermot O'Leary at the National Television Awards, Dermot stepped out of the TARDIS into Albert Square where he was met by Dot. He was shocked to find that she knew the Doctor. Dot explained to him that he was never out of her laundrette. (NOTVALID: Dermot and the Doctor)

She met the Twelfth Doctor at a dinner party with Sprout Boy. (NOTVALID: Sprout Boy meets a Galaxy of Stars)