The Ninth Doctor was an intense and emotional incarnation. We first encounter him after he has travelled alone for a long time, the sole survivor of the Great Time War and the last of the Time Lords. He hides his psychological trauma behind madcap wit and frivolity. At well over 900 years old, his enthusiasm was never dampened and nor was his drive to constantly explore and discover.
It was this Doctor that took Rose Tyler, from the Powell Estate to thousands of years into the future to witness the end of the world; who inspired Charles Dickens to keep writing; and who showed that for once, even against the greatest of odds, everybody could live!
He was capable of great cruelty and anger, dealing harshly with those who chose not to take the right path or make the right choice.
The Ninth Doctor was a brooding but sassy war veteran, riddled with survivor's guilt. His short temper made it hard for him to relate to people. In reality, all of that bluster masked a great affection and empathy, and he was an eternal optimist to his core.
Lookswise, he was probably the most simply dressed of all his incarnations, with close-cropped hair, workmen's boots, and an old beat-up leather jacket worn over a lot of different coloured jumpers. He was also much more street-smart and savvier than some previous incarnations, even outright stating that he doesn't "do domestics".
This fantastic incarnation came to an end shortly after Rose Tyler defeated the Daleks using the power of the Time Vortex from within the TARDIS. In a selfless act, the Doctor saved her life by transferring that dangerous energy into his own body, and in the process triggered his next regeneration. As Rose watched, his body exploded with raging energy…