Matt Smith and David Tennant got on so well while filming the Doctor Who 50th Anniversary Special that they hatched a plan to continue working together on the show, says Steven Moffat.
"They got on like a couple of old women. They just say in the corner and gossiped the entire time," revealed the Doctor Who showrunner.
"By the end of it, Matt told me that he’d worked out this plan that they’d both continue in Doctor Who: do five individual episodes each and three together – would that be ok? It was a nice plan. I think if I’d said yes they’d have gone for it."
However, Moffat admitted that neither star had started out completely confident about bringing their two Doctors together.
"David and Matt, I think... were both quite apprehensive of the other," Moffat told the audience at a Radio Times event earlier this month. "David's continued to watch Doctor Who like the sad old fan he is and so as far as he's concerned Matt's the Doctor. And of course for Matt, you don't believe yourself you're the Doctor, you just think David's the Doctor. So they were both slightly nervous and slightly apprehensive."
Thankfully, those nerves didn't last long, with the pair quickly settling into an energetic dynamic that Moffat believes will thrill fans when the anniversary special hits screens next month.
"The double act between them is sublime," said Moffat. "It’s one of those happy accidents – there’s no reason why they should be, but they are absolutely adorable and hilarious together."
Doctor Who 50th Anniversary Special The Day of the Doctor airs on BBC1, and around the world, on Saturday 23 November.