When Christopher Eccleston bowed out as the Doctor after just one series, it could've been disastrous for Doctor Who.
Audiences had just gotten used to Eccleston's dulcet Northern tones, and now they were going to have to adjust to some new bloke. Similar changes had happened before, sure, but having this one so early in the 2005 revival's lifespan was a major gamble.
But of course, it worked like a charm.
If Eccleston was the initial push that got Doctor Who back onto water, then his replacement David Tennant was the rudder, keeping the show on course for the next four years.
The suit-wearing, hair-spiking, Scottish accent-hiding Tenth Doctor was a force to be reckoned with, and is many people's favourite iteration of the character. However, even the most ardent of Tennant superfans doesn't know everything.
So, put on your 3D glasses and shout "Allons-y!" a couple of times (no particular reason, but it's good practice to do that often) as we dive headfirst into some things you didn't know about the Tenth Doctor.
20. Tennant's Casting Was Hinted At In A Movie
On 16 April 2005 - less than a month after Doctor Who returned to TV after a lengthy hiatus - it was announced that David Tennant would be replacing Christopher Eccleston as the Doctor.
However, the announcement of his casting was very nearly spoiled in the most random of places.
When he was told he got the part, Tennant was rehearsing for a live TV movie version of The Quatermass Experiment, in which he played a character named Dr. Gordon Briscoe.
His fellow castmates clearly knew something was up, because lead actor Jason Flemyng dropped a major hint during the broadcast.
He changed his opening line to Tennant's character from "Good to have you back, Gordon" to "Good to have you back, Doctor ".