The Hitchhiker's Guide to the Galaxy (in-universe)

The Hitchhiker's Guide to the Galaxy was a series of work quoted and referenced several times by the Doctor.

Minor references

• The Doctor once, asked, rhetorically, who had said that "Earthmen rarely invite their ancestors to dinner", which comes from the series. (DW: Ghost Light)

• The Doctor once compared himself to Arthur Dent, the main character of the series, after saving the Earth from invasion in a dressing gown (Dent's trademark dress), and after being awoken from his post-regenerative coma by tea, the character's favourite drink. (DW: The Christmas Invasion)

Behind the Scenes

• Douglas Adams, the writer of the radio show-turned-book turned book series, The Hitchhiker's Guide to the Galaxy wrote a number of Doctor Who serials as well as being a Script Editor of the series during Season 17 of ther series. Consequently, lines from Hitchhiker's Guide found their way into The Pirate Planet and a reference to the Hitchiker's guide character Oolon Coluphid gets a mention in Destiny of the Daleks, which Adams script-edited.

Perhaps by a coincidence, the scene in the third book of the quintilogy - Life, the Universe, and Everything - in which Arthur Dent and a near-Human friend, Ford Prefect, materialise in Lord's Cricket Ground is similar to a similar scene in The Daleks' Master Plan in which the Doctor materialised his TARDIS in the same stadium.

(The third book and radio series in the Hitchhiker's series, Life, the Universe, and Everything was based on a rejected Doctor Who script.

• A man named Arthur Dent said "This rather odd man was lying down in front of a bulldozer in front of my home." on http://www.bbc.co.uk/cult/whoisdoctorwho/sightings.shtml