David Tennant is set to return in Doctor Who's 60th-anniversary celebrations, but he may be playing a creation of the Toymaker rather than the Doctor himself. Next year will be an exciting one for Doctor Who, with Russell T Davies returning as showrunner — and unexpectedly bringing David Tennant and Catherine Tate back with him. The BBC officially announced their return in May, ahead of public filming where set photos would have confirmed it anyway.

Marketing for the Doctor Who 60th anniversary special(s) won't begin until 2023, well after this year's Centenary Special in which the Thirteenth Doctor, Jodie Whittaker, will bow out. For now, the BBC is keeping the 60th-anniversary announcements to a minimum, focusing mainly on exciting casting decisions, including Neil Patrick Harris's mysterious role as a major villain. Still, the lack of detail is ironically leading to ever-more-intense speculation within the fanbase. Davies has addressed it directly in a recent exclusive interview with Doctor Who Magazine; he's always loved the magazine and seems eager to work with it as much as possible going forward.

Related: Everything We Know About Doctor Who's 60th Anniversary

Davies teased how Tennant and Tate could return, presenting a wide range of possibilities. He suggested this could be a sort of "Missing Adventure," a previously-unseen excursion set before Tate's companion, Donna Noble, left the Tenth Doctor's side. Alternatively, perhaps it could be a multiversal adventure, and that "this is a Doctor and Donna from Universe 557, all set to collide with our own." But his third option was most remarkable: "maybe, just maybe, this return is so impossible that it's actually an intricate illusion created by an old enemy of the Doctor's." Surprisingly, this has now become the most likely possibility.

Neil Patrick Harris Appears To Be Playing The Toymaker

Doctor who 60th anniversary true villain toymaker

There have been strong hints Neil Patrick Harris is playing a classic villain who hasn't been seen since William Hartnell's time as the First Doctor. The Toymaker is a powerful Doctor Who foe, last seen in the 1966 story "The Celestial Toymaker." An almost godlike being, the Toymaker was the absolute ruler of an entire dimension, one adjacent to our own. He loved to summon enemies into his dimension to play deadly games, and if they lost they became his pawns for the future. Apparently, he had encountered the Doctor once before, and his clash with the First Doctor was something of a rematch. The first promotional image of Harris's character led to speculation he was playing the Toymaker, and this was supported by set photos from filming in Bristol. The BBC dressed the exterior of one building up as an old-fashioned toyshop, and one Whovian — Connor Mountford — revealed props celebrating him as "Toymaker of the Year." It now looks to be a safe bet.

The Toymaker Has A History Of Rewriting Reality - and Creating False Doctors

Doctor Who Celestial Toymaker

The current Doctor Who era has proved controversial and divisive, in part because of complex retcons. Davies seems to be viewing the Timeless Child retcon as an opportunity to expand the show's lore, drawing in ideas from other mediums; set photos have shown alien creatures from the comics, notably the gangster Beep the Meep and a race known as Wrarths which pursued him. This naturally means he could be drawing on other mediums for inspiration in a similar way — and it's interesting to note one classic Doctor Who comic strip saw the Toymaker create a fake Doctor.

"Endgame" was a four-part story by Alan Barnes, Martin Geraghty, Robin Smith, and Robin Riggs and published in Doctor Who Magazine #244-247. It was actually the first Eighth Doctor adventure published in the magazine after the 1996 Doctor Who TV movie starring Paul McGann, and it saw the Doctor arrive at the village of Stockbridge. He gradually realized this environment had been manipulated by the Toymaker, who was seeking a prize he had found on Earth. The Toymaker was eager to defeat the Doctor at last and actually created a mirror-image Doctor as his competitor — designed to be the Doctor's equal in every way. He could be doing something similar in the Doctor Who 60th anniversary, explaining why the Doctor's attire is slightly different.

Related: Whittaker's Doctor Who Ending Is Being Overshadowed, But Don't Blame RTD

The Toymaker's Real Target Could Be Donna Noble

David Tennant as Tenth Doctor and Catherine Tate as Donna in Doctor Who

All this raises the intriguing possibility that the Toymaker's real target is, in fact, Donna Noble. The Toymaker's vendetta against the Doctor would naturally make his companions of real interest, and ironically Donna is more vulnerable than any other former companion. The Doctor was forced to wipe Donna's memories of their time together after she absorbed a duplicate of his own consciousness because her human mind could not cope with the burden of this knowledge. The Toymaker would possess the power to get around this, however, and he could even sustain Donna's mind to keep her from burning up as he restored her memories.

But the Toymaker may not restore Donna's memories perfectly, simply because he'd consider it entertaining to play around with Donna's perceptions. That would explain why David Tennant's Doctor is wearing a costume that looks ever-so-slightly wrong; the Toymaker could be giving Donna clues to pick up on as her mind recovers, inaccuracies that should make her realize something is badly wrong. To the Toymaker, it would all be part of the game.

What Would This Theory Mean For Doctor Who Going Forward?

Doctor Who Yasmin Finney

Davies has cast Yasmin Finney as a character named Rose, to be introduced in Doctor Who's 60th anniversary but believed to be Ncuti Gatwa's companion when he appears as the next Doctor. There are rumors Rose is in fact Donna's daughter — supported by people who watched the filming and who claim to have heard some dialogue in which Rose called Donna "Mum." If this is the case, then the Doctor Who 60th anniversary special could be Rose's introductory story — the essential backstory in which she first learns of the Doctor, coming to understand the cosmic stakes of her own adventures.

This would be a smart approach, ensuring Rose became a strong viewpoint character through whom the real Doctor could be understood when she finally crosses paths with him. It would also make the Doctor Who 60th anniversary special unlike any story told before in the show's history — one in which Tennant returns, not as part of a multi-Doctor story or a "Missing Adventure," but rather as a pawn of the Toymaker.

More: Will Matt Smith Return For Doctor Who's 60th Anniversary?