The Doctor is a Time Lord: a 900 year old alien with 2 hearts, part of a gifted civilization who mastered time travel. The Doctor saves planets for a living—more of a hobby actually, and the Doctor's very, very good at it.

Steven Moffat
Russell T Davies
Chris Chibnall
Mark Gatiss
Toby Whithouse
Gareth Roberts
Peter Harness
Steve Thompson
Matthew Graham
Neil Cross
Matt Jones
Pete McTighe
Neil Gaiman
Sarah Dollard
Frank Cottrell Boyce
James Moran
Malorie Blackman
Phil Ford
Richard Curtis
Robert Shearman
Murray Gold
Delia Derbyshire
Segun Akinola