A satyr was a lifeform that could be found on the planet Megas-Tu. They were humanoid, with a furred lower half with tails and hooves, while the upper half was much like humans', except for horns and a lack of nipples. Like other Megans, they were capable of using magic.
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")