As a character, the Ninth Doctor is less of a central heroic figure than an enabler, encouraging his companions and other people he meets to act upon their more positive impulses. Those he meets often credit him with making them better people. He uses this quality alongside his intelligence and the information he gathers to inspire and allow others to act to end the dangers they face, rarely taking direct action himself.
The Doctor's ninth incarnation was perhaps the most gritty, and informal, masking a lonely, guilt-ridden and melancholic personality with a jovial, witty, forthright and almost manic exterior. Similar to the Fourth Doctor, he would often make jokes in the face of danger, but then become grim and serious when on his own. Like the Sixth Doctor, he also tended to be fatalistic at times to the point of near-panic. Despite being impatient with humans, whom he often referred to as "stupid apes", the Ninth Doctor was far more tactile with, and reliant upon, his human companions than previous incarnations.
In contrast with his successor and in common with his third, fourth and sixth selves, the Ninth Doctor did not shy away from using force in situations he would deem necessary.
On several occasions, the Doctor indicates that he is 900 years old, the same age as the Sixth Doctor claimed to be. The Ninth Doctor's catchphrase, used in a variety of manners, and sometimes ironically, was "Fantastic!" (In 2007, Eccleston joined the cast of the American series Heroes; in the episode "The Fix", Eccleston's character Claude utters "Fantastic!" in the same occasionally ironic fashion as the Ninth Doctor.)