Doctor Who, a BBC science fiction television series that has been running for over 50 years, is extremely popular with both children and adults. It has also been adapted to audio dramas (Big Finish Productions), as well as novels, comic books, and a single full feature film. The show is about an alien from planet Gallifrey, who calls himself the Doctor. The Doctor has a time machine, called the T.A.R.D.I.S. (Time And Relative Dimension In Space), which looks like a blue police call box. The T.A.R.D.I.S. is bigger on the inside than the outside and can travel through both time and space, sometimes even going where the Doctor wants it to go.