Steven Moffat reveals how the fifth season of Doctor Who would have gone had David Tennant stayed on as The Doctor. If there is one thing that fans of Doctor Who have to learn, it's that they cannot get too attached to anyone. Any show which airs for as long as Doctor Who has a certain amount of attrition, cast and crew moving on for various reasons and new people coming in to replace them. But when you add in the show's main character being an alien species that regenerates upon death, changing names and faces are inevitable.
The show is going through one of those changes right now, with an entirely new cast and showrunner about to begin. Much of the focus has been on the new Doctor played by Jodie Whittaker - the first woman to play the role. But behind the scenes there is another shakeup happening, as showrunner Steven Moffat steps aside and Chris Chibnall takes over. Moffat worked as a writer for the first four seasons of the revived series before taking over as showrunner with season five. He's been a polarizing leader for the series, responsible for some of the show's most popular episodes, and some rather unpopular ones as well. He's certainly ending on a high note however, with the well regarded tenth season.
In an interview with The Doctor Who Fan Show, Moffat explained how his first year as showrunner could have gone very differently. When Moffat was in the process of taking over, lead actor David Tennant was not sure if he wanted to stay another year or not. So Moffat explained to him what the story for season five would be like with Tennant as The Doctor.
In a lot of ways, the season would have been similar to the one we ended up having, starring Matt Smith as the 11th Doctor. The TARDIS would have still crashed in the yard of young Amelia (Amy) Pond. She would have found it, and The 10th Doctor regenerating. Then he would have flown away in the TARDIS. When she encountered him years later as an adult, he was a younger version of himself, from an earlier point in time. The season would have continued bringing The Doctor and Amy to the point where they first met - right before his death and regeneration. After thinking it over, Tennant decided to move on after all, Smith was cast, and the moment Amy Pond met the Doctor was immediately after he regenerated - not before.
While it's a shame to never have gotten the season with the 10th Doctor and Amy Pond, it's hard to be disappointed with Smith's introduction in season five, or with the friendship between 11 and Amy. The writers of Doctor Who have to be ready for the show's constant cast changes, and it sounds like Moffat was good to go on whichever decision Tennant went with. If he's taught Chibnall to be that prepared as well, season eleven is probably off to a good start.
Source: The Doctor Who Fan Show