Peter Capaldi as the current Doctor Who: would the role work with a female?
Doctor Who star Sylvester McCoy has declared time travel is a man's world, insisting that the iconic TV time-traveller should always be played by a male actor.
McCoy, who played the seventh incarnation of Doctor Who in the 1980s, has told British press that he was "not convinced by the cultural need" for a female Doctor Who.
That observation comes as fans of the series continue to debate whether a future incarnation of The Doctor could be female, and whether indeed Time Lords can change sex when they "regenerate".
The seventh Doctor Who, Sylvester McCoy, once described the Doctor as a male character, "just like James Bond".
The notion of "regeneration" was created in 1966 when actor William Hartnell, who had played the first Doctor Who for three years, became ill and was unable to continue in the role.
The role was re-cast with Patrick Troughton with an "in-universe" explanation that Time Lords could "regenerate"; that is, cast off an old body for a new one, when the old body was damaged beyond repair.
That twist has now seen a long list of actors play the role, including Jon Pertwee, Tom Baker, Peter Davison, Christopher Eccleston, David Tennant, Matt Smith and, currently, Peter Capaldi.
The Doctor did regenerate into a woman played by Joanna Lumley in a one-off charity special that is not considered part of the Who canon.
More than a dozen men have played The Doctor, if you include stage productions, feature films and other "non-canon" interpretations of the character.
"I'm a feminist and recognise there are still glass ceilings in place for many women, but where would we draw the line?" McCoy, 71, said.
"A Mr Marple instead of Miss Marple? A Tarzanette?"
Would the dynamic of the Doctor and his companion be lost if a female took the role?
"I'm sorry, but no, Doctor Who is a male character, just like James Bond," he added.
"If they changed it to be politically correct then it would ruin the dynamics between The Doctor and the assistant, which is a popular part of the show."
Though there have been a few "in-universe" clues about gender-switching Time Lords, the debate has raged for many years in the real world.
It has also been nudged along by several other characters in popular culture re-interpreted with a different gender, in part due to the growing influence of comic books, where such changes are more easily accepted, and "re-interpretations" of characters are more frequent.
Those include re-casting the roles of Starbuck and Boomer in the Battlestar Galactica remake as women, and an announcement from Marvel that they plan to feature a female Ancient One in Doctor Strange and cast a female Captain Marvel.
Marvel has also changed the gender of Thor, one of its flagship characters, with a current comic book series in which the hammer Mjölnir - which can only be used by the god Thor - is wielded by a woman.
The TV series Elementary, which reboots the Sherlock Holmes story, features a female partner to Holmes, Joan Watson, played by Lucy Liu; in the original books and almost all other reboots, Holmes' partner, Watson, is male.
And in the James Bond universe, the character of M - the head of MI6 - has been played by both men and women, notably Bernard Lee, Robert Brown, Judi Dench and, most recently, Ralph Fiennes.
In a one-off charity special, Doctor Who and the Curse of the Fatal Death, The Doctor did regenerate into an incarnation played by actress Joanna Lumley, but the events in the special are not considered series "canon".
The biggest clue came in the most recent season of the series, in which The Doctor's long-standing nemesis The Master returned in a female body, now known as The Mistress, or "Missy", played by Michelle Gomez.
The Master's three best known previous incarnations were played by Roger Delgado, in the 1970s, Anthony Ainley, in the 1980s, and John Simm, on the post-2005 reboot series.
The show's producer Steven Moffat, quizzed on the issue at this year's Comic-Con International convention in San Diego, said he was not opposed to the idea.
"Well, I think my opinion is fairly obvious from the show, isn't it?" he said. "What I think about the possibility and whether it would work or not.
"I think I've expressed myself about as clearly as I could, in the context of the show," he added.
"If you're not reading the subtext, then I'll lend you. But believe me, some people aren't reading that subtext, 'cause it's too subtle."
Most commentators have interpreted his remarks as an endorsement for the possibility of gender change, particularly as it is on his watch as the Doctor Who showrunner that a Time Lord - The Master - has changed gender.
Moffat also noted that the first line of dialogue he wrote as the show's executive producer was Matt Smith's Doctor, in the wake of his regeneration, wondering if he was a girl.
In the past, the series has featured a number of high-profile female Time Lords, or Time Ladies, such as Romana (Mary Tamm, later Lalla Ward), The Rani (Kate O'Mara), Chancellor Flavia (Dinah Sheridan) and The Inquisitor (Lynda Bellingham).
But prior to The Master's regeneration into The Mistress, no Time Lord has, on screen, explicitly changed gender between regenerations.