A satyr is a type of lifeform that can be found on the planet Megas-Tu. It has horns that, along with its lower body, look like those of an animal, although it also has a recognizably humanoid face, chest, arms and neck.
In 2269, a young boy satyr suddenly appeared before James T. Kirk, when Lucien took Kirk, Spock and Leonard McCoy to Megas-Tu, Lucien's homeworld. The child satyr was conjured up by Lucien (as was a wind that downed Kirk) in response to Kirk asking why he and his fellow officers from the USS Enterprise had been brought to the planet. The boy had a spinning top that stopped rotating as Kirk looked at the child and Lucien then commented, "Children will play." (TAS: "The Magicks of Megas-Tu")