Photo credit: http://www.denofgeek.com/television/392180/doctor_who_bbc_releases_david_tennant_to_matt_smith_image.html
Again, very old, but I have only just discovered it. An interview with Matt Smith following the announcement that he had been cast as the new Doctor. It shows very clearly where the Doctor's quirkiness comes from ie Matt himself!
Matt Smith as the Eleventh Doctor:
Matt Smith portrays the Doctor as an energetic, eccentric and lively soul who possessed a sense of arrogance and a short temper. While the Doctor was usually cheerful and full of manic energy, traits he shared with his previous incarnation, he also had a darker side and was capable of becoming furious if his loved ones were threatened. The Doctor was also less forgiving and more aggressive than his previous incarnation showing considerable hatred towards his arch enemies, the Daleks. The Doctor is also notable for his self loathing, claiming that he was "a stupid selfish man" and even saying that he hated himself more than anyone else in the Universe.
The Doctor's outfit is a brown tweed jacket with elbow patches, bow tie, braces, rolled up trousers and black boots. He frequently refers to his affection for bow ties, often proclaiming "Bow ties are cool."