Horse

The horse is large mammal native to Earth. Humans used horses as transportation for thousands of years prior to the invention of motorised transport.

The Trojan War ended when the Greek army, on the Doctor's advice, constructed a giant wooden statue of a horse, hid inside it and presented it to Troy. (DW: The Myth Makers) The Trojan Horse would go on to become a frequently used metaphor for hidden danger.

Horses are also known to have evolved on other planets, such as
 * Cheetah World (DW: Survival),
 * Telos (BFA: Spare Parts),
 * presumably, Augea. (TDA: Sting of the Zygons)

A purple horse with yellow spots was a delegate at the Third Inter-Galactic Peace Conference. (DW: Frontier in Space)

Appearances

 * DW: Marco Polo
 * DW: The Reign of Terror
 * DW: The Crusade
 * DW: The Gunfighters
 * DW: The Smugglers
 * DW: The Highlanders
 * DW: The War Games
 * DW: The Time Monster
 * DW: The Masque of Mandragora
 * DW: The Visitation
 * DW: The King's Demons
 * DW: The Awakening
 * DW: Survival
 * DW: The Girl in the Fireplace