The Girl Who Loved Doctor Who (in-universe)

In a parallel universe where the Doctor's life was a TV show, Matt Smith began filming a secretive TV story in 2013 about his character coming to the "real world."

By circumstance, the Eleventh Doctor fell into this universe directly before filming began, eventually crossing paths with Smith at Doctor Who Con 2013. Smith, who believed the Doctor to be a cosplayer, remarked that a scene just like this meeting should be in the episode, and that he'd ask Steven Moffat to write it in.

Filming of the final scene of the episode, intended to feature the Doctor fighting a Cyberman, turned hectic when the scene played out as they attempted to film it, as a real Cyberman attacked the man playing one. The Eleventh Doctor managed to send the real Cyberman back to his universe, saving the cast and crew.

Matt Smith soon realized the Doctor was real and the two had a conversation. The Doctor recommended Peter Capaldi as a fitting actor to replace Smith. Smith promised to pass this along to Steven. As the Doctor left in The TARDIS, the crew continued to film, noting that they were going to "save a fortune on special effects." (COMIC: The Girl Who Loved Doctor Who)

Behind the scenes
In the plot of The Girl Who Loved Doctor Who, it is made explicit that the events of the comic are about to be filmed as a TV story, seemingly indicating the story would be a bonus special after TV: The Name of the Doctor and before TV: The Day of the Doctor. The name of the TV story is not stated in the story, but it is fair to presume that it would have been the title of the comic itself.