He has three hearts. He is hundreds of years old. When he dies, he regenerates into a new body. He wasn't even born on Earth.
Yet all the qualities that we love about the Doctor are as foreign to us as love and hate.
A few minutes ago I finished the two-part story written by Paul Cornell for Doctor Who: Human Nature and The Family of Blood. Both of the episodes explored what is, to me, the most fascinating aspect of this series: the Doctor's character. While being chased by a family of shape-shifting aliens who wish to consume his Time Lord essence in order to gain immortality, the Doctor arrives in 1913 England where he uses a device to change his entire physiology - every single cell - to that of a human. The Doctor undergoes the transformation because the Family (the previously mentioned aliens) is able to smell him from a long ways off, due to his own alien nature. Cue David Tennant proving how good of an actor he is.
