The Doctor is a Time Lord - one of an elite race of beings from the planet Gallifrey, outwardly humanoid but with many differences. Time Lords possess two hearts and a respiratory bypass system, have an internal temperature of 60 degrees Fahrenheit, and they have the unique ability to regenerate their bodies when the current one becomes worn out or irreparably damaged. This does not mean that a Time Lord simply heals his body, but rather that his entire cellular structure is rebuilt - resulting not just in a completely new body, but also a completely new personality and temperament.

Because of this ability, the Doctor has worn a number of different faces over the years. Each version of the Doctor displays new traits and personality facets. Yet despite all of the changes, a number of things stay consistent. The Doctor fled Gallifrey in a stolen TARDIS because he was tired of his people's policy of noninterference and wanted to make a difference. His primary motivation is still to protect the universe from the multitude of evils that plague it, and this is supplemented by a healthy desire for travel and learning.

The Doctor is basically a nonviolent man, although he is willing to resort to such methods if he feels that the situation warrants them. But he is always conscious of the repercussions of his actions, and is careful not to overstep his boundaries. Still, he feels that some rules are made to be broken, or at least stretched, and enjoys defying authority. In fact, the Doctor has little respect for typical authority figures - he must first be convinced of their worthiness.

An extremely intelligent being, the Doctor is amazingly talented in deduction, reasoning, and logic. His knowledge of most areas of science, mathematics and history is almost unparalleled, and his ability to apply his knowledge frequently comes in very handy for him. It is simple work for the Doctor to piece together a mystery, construct a complex device to defeat an enemy, or work out the purpose of something he has never before seen.

The Doctor is angered by cruelty, tyranny and injustice. He is very protective of the people in his care. He fights for the individual while focusing on the bigger picture. He has a definite sweet tooth. And Earth is quite his favorite planet, though he often wonders why.

Now that you know a bit about the Doctor as a whole, delve into each of his incarnations to learn a bit more about what - and who - he is made of.