1) The Doctor is a timelord, from Planet Gallifrey, and to date is currently in his 10th incarnation.
2) 10 actors have played the Doctor, which is explained by him being able to regenerate.
3) The Daily Mail has dubbed the character, 'Britains Favourate Alien'.
4) The Doctor is currently played by David Tennant, but in late 2008 he annouced he was leaving, and so will be replaced in 2010 by Matt Smith.
5) He travels through time and space in an internally vast time machine called the TARDIS — Time And Relative Dimension(s) In Space, which is an acronym the Doctor's granddaughter, Susan, claims to have invented.
6) Not much is known about the Doctors childhood apart from in 'The Girl In The Fireplace' it was stated by Madame de Pompadour, whilst reading his mind, that he had a lonely childhood.
7) However in 'Smith and Jones', the Doctor was asked wether he had a brother, in which he replied, "Not anymore".
8) In the 10th Doctors finale later this year, it has been reported that the Doctor's mother will star in it and that it will be revealed that the Master is his brother.
9) In 'Fear Her', the Doctor did metion to Rose that he was a farther once but quickly changed the subject.
10) The Doctor has and always will be a mysterious character, but after Journeys end the Doctor rengenerated into two, so in another universe their is a second human Doctor.