Little Nell

Little Nell was a fictional character created by Charles Dickens. On Christmas Eve 1869, the Ninth Doctor told Dickens that her death scene "cracked [him] up". (TV: The Unquiet Dead)

Conversely, Henry Gordon Jago told his friend Professor George Litefoot in the 1890s that he was "beside [himself] when Little Nell died." (AUDIO: Beautiful Things)

Behind the scenes
The mention of this character implied that the novel, The Old Curiosity Shop, also exists within the Doctor Who universe. The novel was later referred to by Jenny Flint in AUDIO: A Photograph to Remember, though Little Nell's connection to the story was not mentioned.