Loch Ness Monster

The Loch Ness Monster, also known as Nessie, was a mysterious animal claimed to inhabit Loch Ness, a lake in Scotland. (TV: Terror of the Zygons)

History
The Fourth Doctor once briefly encountered what appeared to be the Loch Ness Monster while strolling on the shores of Loch Ness. The creature he saw had a long, thin neck which protruded eight or ten feet from the surface of the loch, and resembled a plesiosaur. It was about thirty foot long and had four flippers. It briefly regarded the Doctor before disappearing again, leaving no evidence that it had ever been there. The Doctor began to wonder if the encounter had really occurred or if he had hallucinated it. (PROSE: Doctor Who Discovers Strange and Mysterious Creatures)

One creature that was believed to be the Loch Ness Monster was the Skarasen, which was brought to Earth by the Zygons circa the 12th century and subsequently inspired legends of a monster associated with the place. (TV: Terror of the Zygons)

Another possible source for the belief in the monster was the Borad, who was brought to Earth from the planet Karfel via the Timelash in 1179. (TV: Timelash) However, two Celestis investigators killed him shortly after his arrival in Scotland before the Zygons arrived. (PROSE: The Taking of Planet 5)

In another account, Loch Ness had not one or even two, but thousands of monsters. (PROSE: Christmas on a Rational Planet)

By the late 21st century, new mapping technologies had thoroughly demystified rumours of cryptids hiding around the globe. In response to this, a cryptozoologist joined Faction Paradox as Father Stendec and began repopulating history with cryptids. His favourite project was in Loch Ness, where he settled at least five species of dinosaur. Some of these he had specially designed from parts of other dinosaurs. (PROSE: The Book of the War)

Behind the scenes

 * In the unproduced Doctor Who movie, Doctor Who Meets Scratchman, the Doctor was mentioned as having found the Loch Ness Monster in a reference to the events of Terror of the Zygons.
 * The Loch Ness Monster could have appeared in "Doctor Who and the Monsters of Ness", a pilot episode starring David Burton made by an independent company in the 1990s. However, this is widely considered as a hoax.