It may be one of the BBC's most popular shows, but a newly-released internal memo from the British broadcaster reveals Dr Who's first transformation in 1966 was modelled on a bad LSD trip.
The vastly popular BBC series starring a time-travelling doctor was first broadcast in 1963 and is now in its 31st season.
However, every few seasons a different actor plays the main character.
The memo, released this week, says the transformation represents the "hell and dank horror" of a drug experience gone wrong.
Nearly 760 episodes of the series have been made, and one television movie.
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Matt Smith, who plays the show's current protagonist, is the title character's 11th incarnation.
