Snake

Snakes were a variety of reptiles of the suborder Serpentes on Earth. They were often seen as fearsome and representative of evil.

History
A snake from Brazil was one of the animals on board the Ark. (TV: The Ark)

A type of giant snake was native to Metebelis III at some point in its history. (TV: The Green Death)

Giant purple Ice Snakes lived on Centuria. (COMIC: Enemy Mine)

The Church once fought lava snakes. (TV: The Time of Angels)

A giant species of snake called the Oroborus was able to consume time. (TV: Oroborus)

Another giant species of snake known as the Sythaks were native to the swamps of Palliox, a planet near Trion. In 1905, the travelling showman Thaddeus P. Winklemeyer had two Sythaks in his freakshow. (AUDIO: Freakshow)

In a jungle on an unnamed planet, Gillian was threatened by a hooded snake, but the First Doctor saved her by throwing his coat over it. (COMIC: The Didus Expedition) As part of his magic act for the Gods of Ragnarok in the Dark Circus, the Seventh Doctor appeared to conjure a snake, then transform it into his umbrella. (TV: The Greatest Show in the Galaxy)

Colony Sarff was a creature comprised of many snakes working together to mimic one humanoid individual. (TV: The Magician's Apprentice/The Witch's Familiar)

Food
On Thoros Beta, sand snakes were consumed by the Mentors, such as Kiv. (TV: Mindwarp)

Emotive responses
Styre's experiments into fear on Sarah Jane Smith caused her to hallucinate a snake on her arm. (TV: The Sontaran Experiment) Polly Wright was also always afraid of snakes. (AUDIO: House of Cards)

When the Mara took physical form away from Dark Places of the Inside it took the form of a giant snake, both as a tattoo and as a physical snake. (TV: Kinda, Snakedance)