"The Once And Future King" is about a young man, Gary Pitkin (Jeff Yagher), who makes his living as an Elvis impersonator.
One day, Gary is in a car accident. He wakes up, dazed but alive, and is greeted by a man who looks just like him - and who says "You look all shook up." The other man is Elvis (Yagher in a dual role). Gary has apparently been transported back in time to meet his idol.
Elvis, for his part, thinks that Gary is the reincarnation of his dead twin brother. Elvis eagerly plays for Gary some of the music he is planning to record. Gary is horrified to hear easy-listening ballads coming from the rock singer he has idolized all his life. Gary tries to play some of the songs that he remembers, but Elvis doesn't want any part of it, thinking it's the devil's music. Gary becomes angry and calls Elvis a "son of a bitch", but Elvis takes it literally and attacks Gary for supposedly insulting his mother. In the ensuing scuffle Elvis is accidentally impaled on a piece of wood and killed.
Realizing what must happen next, Gary buries Elvis and assumes his identity. Gary then goes on to live Elvis' life and career - recording all the songs, doing all the films, as he remembers Elvis doing them. The episode concludes on the Las Vegas strip, where an older Gary (as Elvis) is recounting the entire story to a groupie.