Pig

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

Certain religions, like Islam and Judaism, forbade 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 and biological features similar to humans. In the 1930s, the Cult of Skaro turned the less intelligent people they captured into Pig slaves, humanoids with pig-like features, to work for them. (DW: Daleks in Manhattan/Evolution of the Daleks)

In 2006, a pig was augmented by the Slitheen family as a hoax alien invader. It was then planted in a ship to act as a diversion from the family. (DW: Aliens of London)

In the 51st century Mr Sin, a cyborg with the brain of a pig, was created. (DW: The Talons of Weng-Chiang)

The Doctor once declared that a number of planets were home to a variety of pig that could fly. (GN: The Only Good Dalek)

Sock Pig was a toy made from a sock in the form of a pig. It was brought to life by the Anima. (ST: Sock Pig)