Dream casting for the next Doctor began the second Peter Capaldi announced his intent to depart Doctor Who at the end of its current tenth season. Rumors started swirling about his replacement probably only a few seconds later.

It's of the most unique situations on TV; because the Doctor is able to regenerate, multiple actors have played the role of the heroic Time Lord from Gallifrey over the years. When one actor departs, another slips into their shoes and the entire cycle repeats itself. This essentially means the possibilities are limitless, provided no one pulls the plug on the long-running science fiction drama, which has happened before.

Doctor Who: 9 people we'd like to see become the next Doctor

But with Capaldi's exit looming at the end of the season, fans are dying to know who'll step into the role of the Thirteenth Doctor. Apparently it's such a secret that current showrunner Steven Moffat, who will depart the series alongside Capaldi, claims even he doesn't who's next.

"You'll have to ask [incoming showrunner] Chris Chibnall," Moffat tells TVGuide.com. "I honestly am out of the loop and have purposefully remained so on what Chris is up to with the recast, because my advice to him was you only tell people what you're thinking if they absolutely need to know it. I don't need to know it so don't tell me or I might accidentally say something on the bus. I have absolutely no idea what the plans are."

Peter Capaldi, <em>Doctor Who</em>Peter Capaldi, Doctor Who


Since the sci-fi series was revived in 2005 by Russell T. Davies, thirteen men have taken on the role of the Doctor, including the late John Hurt, as the War Doctor in the show's 50th anniversary celebration. For many fans, it's well past time for a female or a person of color to take on the role. Moffat admits that the idea has "been contemplated before and it didn't work out."

Doctor Who will address race this season

But when asked about Capaldi's regeneration — which the Scottish actor recently revealed to the New York Times will not be as straightforward as in year's past — Moffat was predictably quite mum on that front too. However, he did note they're not treating it casually and also spilled a few details on the difficult process he faces as the series prepares for yet another era to begin.

"The problem I face — or anyone in my job faces with a regeneration — is that we've got to go on an adventure during which [the Doctor is] horrifically injured or something happens to him that causes him to regenerate," says Moffat. "Now, what's special about that? Just about any Doctor Who story could viciously injure him. How do you make it special? How do you make it interesting? Given that it's a story we've seen before many times and not that long ago, how do we make this time different?"

"In the end, what we're accommodating is a necessary recast," he continues. "It's the world's most imaginative response to a staffing problem. You can't go completely mad on this. We're essentially shipping one actor out and shipping another actor in. We do try to make it different every time and I would argue that it is different each time."

Doctor Who airs Saturdays at 9/8c on BBC America.

Additional reporting by Alex Zalben