Pig

A pig is a four-legged animal native to Earth.

References to Pigs

 * In 1930s New York, the Cult of Skaro turned the less intelligent into Pig slaves (DW: Daleks in Manhattan/Evolution of the Daleks)
 * In 2006, a pig was augmented by the Slitheen as a hoax alien invader. (DW: Aliens of London)
 * By year 5000 some cyborgs used the brain of a pig, Mr. Sin was one such cyborg from this period. (DW: The Talons of Weng-Chiang)