Catherine Tate thought Doctor Who specials would end with "terrible thing"

It covers The Giggle, which made Doctor Who history when the Doctor bigenerated, resulting in David Tennant's Fourteenth Doctor existing alongside Ncuti Gatwa's Fifteenth.

Fourteen then decides to stop travelling in the TARDIS full-time, instead staying with Donna and the Nobles.

The final scene shows the Nobles happily eating lunch in the garden together - and even includes a mention of Wilf after Bernard Cribbins's surprise return before his death last year.

Speaking about that surprise ending, Tate said: "It was so not what I was expecting. I thought there was going to be a massive, terrible final thing. [But] to end in the garden eating crumble is, of course, exactly where they should be."

Davies also revealed in the documentary that the bigeneration is something he's been considering for years.

He said: "Everyone’s expecting David Tennant to die and for Ncuti to be reborn as the new guy and, instead, I’ve been dying to do this for years - he splits in half, so you have two Doctors.

"That moment on screen of them going [pop] is astronomically exciting. It is a happy ending and David Tennant survives."

Of course, the bigeneration has bigger implications for the entire series, with Davies saying that when David Tennant and Ncuti Gatwa split into two, "a whole timeline bigenerated".

The writer then suggests that each previous regeneration was impacted by the bigeneration, with every 'old' Doctor now surviving his demise in a splinter timeline.

"I think all of the Doctors came back to life with their individual TARDISes, the gift of the Toymaker, and they're all out there travelling round in what I'm calling a Doctor-verse."

As for how this will impact the future of Doctor Who, only time will tell.

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