Pig

A pig is a four-legged animal native to Earth. They were domesticated from wild boars and were raised mainly for their meat. Certain religions, like Islam and Judaism, forbid the eating of pigs, a practise that continued and evolved even after pigs went extinct. (BNA: The Mary-Sue Extrusion)

Pigs were also used for a variety of experiments, likely due to their prevalence. In 1930s New York, the Cult of Skaro turned the less intelligent people they captured into Pig slaves to work for them. (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) In the 51st century, a cyborg with the brain of a pig (Mr. Sin) was created. (DW: The Talons of Weng-Chiang)