The Doctor (The Thief of Sherwood)

According to one account, the Doctor existed only ever as a fictional creation, as the eponymous character in the BBC science fiction series Doctor Who. (PROSE: The Thief of Sherwood) This was also true in multiple meta-fiction universes. (COMIC: TV Action!, The Girl Who Loved Doctor Who)

The titular character was also referred to as "Dr. Who" in the credits for the show and in a synopsis for Radio Times. (PROSE: The Thief of Sherwood)

In 1964, the Doctor was played by William Hartnell. Tom Baker played the Doctor during the 1970s. (PROSE: The Thief of Sherwood)

Fictional biography
The Doctor was a Gallifreyan. (PROSE: The Thief of Sherwood) He initially traversed the universe with his granddaughter Susan Foreman and later gained two other companions in Ian Chesterton and Barbara Wright. The latter described being "shanghaied into time and space" by the Doctor.

Barbara wrote to her Auntie Margaret about her recent experiences of being poisoned by radiation, hailed as a goddess, possessed by an alien brain and let down by a Frenchman. They had also encountered the Daleks.

On one occasion, the Doctor landed the TARDIS in an abandoned medieval castle during the time of Robin Hood. He was captured by the Merry Men. The Doctor spared Ian from being executed by the Sheriff of Nottingham by posing as an monk. He then secured Ian's release by convincing the Sheriff he could make gold from base substances. When the Sheriff came to observe the Doctor's demonstration the Doctor set light to the mixture causing an explosion and knocking them both unconscious. The Doctor escaped and the Merry Men attacked the Sheriff causing him to flee. After this, the Doctor set the controls in the TARDIS for 1964 but warned of a build up of pressure outside the craft, leading to their next predicament. (PROSE: The Thief of Sherwood)

Behind the scenes
As well as in stories that give no indication of happening in a different universe, the Doctor existing solely as a character in Doctor Who has been explored in other sources. The Eighth Doctor visited a universe where he discovered his fourth incarnation as a fictional character in TV Action! and the Eleventh Doctor visited a similar universe where he found himself fictional in The Girl Who Loved Doctor Who. Of course, as a significant part of popular culture and Earth history the Doctor as a character in fiction has been explored from other stories within the Doctor's universe such as Sarah Jane Smith's Doctor series.