"The Once and Future King" is the first segment of the twenty-fifth episode, the first episode of the second season (1986–87) of the television series The Twilight Zone.

Gary, an Elvis impersonator, opens in a smoke-filled lounge, singing "Heartbreak Hotel" in Elvis' signature 1950s gold lamé suit. Much to Gary's chagrin, his performance receives mediocre applause. Afterward, Gary is in his dressing room when his manager, Sandra, walks in. Sandra tells Gary that she was able to book him into a small hotel on the Las Vegas Strip. The mere mention of Las Vegas drives Gary into a rant about how Vegas killed Elvis and how he didn't have to make the same mistakes he made just because he looked like Elvis. He laments about how it was great music, but she reminds him, it was...but it's not "his" music.

As Gary is driving down the road, he sees an incoherent driver coming the opposite direction swerving left and right. To avoid hitting the driver, Gary steers off the road, only to have his car flip upside-down. Gary awakes the next morning and sees the damage done to his car. He then gets up, grabs his guitar and starts thumbing for a ride. A man in an old pickup truck sees Gary and pulls over. Gary runs to the passenger-side door, and to his shock, sees that the man resembles Elvis. He offers Gary a ride, saying "You look...all shook up." When Gary opens the door, the sign on it says "Crown Electric Co.", which was the company Elvis worked for before getting his first recording contract.

They break the ice by talking about how they're both musicians. As they're talking, Gary looks over and sees an old Chrysler DeSoto drive by. He then picks up a newspaper sitting on the floor and looks at the date: July 3, 1954. Gary comes to the realization that the man sitting next to him not only looks like Elvis Presley, but that he actually is Presley. Gary begins thinking that all of this is a hallucination resulting from his accident the night before.

...
Wikipedia