A new development in "Doctor Who" may affect the future installments of the popular show.

Veteran director Joss Whedon revealed during a Q & A session with Nerd HQ 2016 that he had some reservations writing an episode for the series, though he is open to the possibility of still doing it in the future.

During the session, a fan asked Whedon if he would be down on board the series wagon as a writer.

"I'd have to do a lot of research. Like watch 40 years of television. I've seen some of it," he said.

Whedon cited that aside from the long history of the series, filling the shoe of current showrunner and writer Steven Moffat would be a huge challenge.

"It would be very daunting to follow in the footsteps of Moffat and the guys," he said.

However, the director suggested towards the end of the interview that he might still take on the project, but on one condition.

"Check back with me when 'The Doctor' is a she. Or Idris Elba," he teased.

His statement delighted the people behind the series who are planning to diversify the cast once more. Last month, Moffat revealed that the role of "The Doctor" was offered to an actor of color, but it unfortunately did not work out. However, the casting of Mackie could be an indication that change is coming for the show.

"I certainly don't think there's ever been a problem with making the Doctor black, which is why it should happen one day," said Moffat.

Production on the new season of "Doctor Who" is already in progress. Recent reports suggest that the cast and crew of the series are currently filming in Valencia, Spain.

The new season of the series is expected to premiere sometime in 2017.