The Seventh Doctor, Ace and Bernice Summerfield accidentally faced Cthuhlu in 1915 when trying to visit Ernest Hemingway in nearby Key West, Florida. Once there, they met Francois Lacombe, a native of the Alsace region of France. While there, they prevented Mait Lemaitre from summoning Cthulhu.
Cthulhu, like a number of other Great Old Ones, had been on Earth at some point following the Silurians going into hibernation. Centuries of warfare had damaged the planet and Cthulhu’s only recourse was to entomb itself in a stone crypt deep within the planet in the caverns underneath Hispaniola. Its separated consciousness travelled along the time winds while its sleeping body retained its subconscious mind. The two could not be merged until an alignment of the stars as they had been when Cthulhu was whole. Due to the universe’s constant expansion and evolution, perfect alignment would be impossible and Cthulhu needed others to perform rituals that would give the subconscious additional focus in drawing the consciousness from the Time Vortex.
When the correct alignment occurred in 1915, Cthulhu’s body was able to dream for several days and this created a pervasive psychic background at .338 microbars of pressure. Gilles Lemaitre, using the vodoun ritual of Wete Mo Nan Dlo, attempted to restore Cthulhu. Cthulhu, in turn, helped Mait in his plans to create an army of zombies and a device to control them. Before Mait could awaken Cthulhu, the Doctor managed to set explosives in the tomb which killed Mait and resealed the Great Old One’s tomb.
The Great Old One in Haiti wasn’t identified until the novel All-Consuming Fire in which the Doctor associates a number of past enemies with specific Great Old Ones. A brief speech by the Seventh Doctor defines who the Great Old Ones are. This ties together several creatures encountered in Doctor Who, and binds them in a common group with other mythologies, such as the H. P. Lovecraft Cthulhu stories. He says that the following are “Great Old Ones”: Cthulhu, Gods of Ragnarok, Nyarlathotep, Dagon, Fenric (otherwise known as Hastur the Unspeakable), Yog-Sothoth (better known as the Great Intelligence), and Lloigor.
Yes, my friends … Doctor Who can easily be popped into a session of the Call of Cthulhu role-playing game.