Spock, commonly Mr. Spock (sometimes popularly referred to as: Spock, son of Sarek), is a fictional character in the Star Trek media franchise. Spock was first portrayed by Leonard Nimoy in the original Star Trek series, and also appears in the animated Star Trek series, a two-part episode of Star Trek: The Next Generation, eight of the Star Trek feature films, and numerous Star Trek novels, comics, and video games. Spock serves aboard the starship Enterprise, as science officer and first officer, and later as commanding officer of two iterations of the vessel. Spock's mixed human-Vulcan heritage serves as an important plot element in many of the character's appearances. Along with Captain James T. Kirk and Dr. Leonard "Bones" McCoy, he is one of the three central characters in the original Star Trek series and its films. After retiring from Starfleet, Spock serves as a Federation ambassador, contributing toward the easing of the strained relationship between the Federation and the Klingon Empire. In his later years, he serves as Federation ambassador to the Romulan Star Empire and becomes involved in the ill-fated attempt to save Romulus from a supernova, leading him to live out the rest of his life in the parallel timeline introduced in Star Trek (2009).