An alter ego is a second personality, and in show business it means a character a performer invents and inhabits on stage, often far bolder than the person who goes home afterwards. The phrase is Latin, literally another ego: Cicero used it for a trusted friend, a second self, and English borrowed it in the 1530s.
Pop has made a habit of building alter egos and then retiring them with flair. David Bowie toured as the glittering Ziggy Stardust and, on 3 July 1973 at London’s Hammersmith Odeon, announced from the stage that this was the band’s last show, leaving many fans convinced he was giving up live music altogether; it was Ziggy who was bowing out. Beyoncé gave her fiercest stage self the name Sasha Fierce and an album title, then told Dazed and Confused that she no longer needed her. Alter egos may be the only performers who reliably keep their farewell promises.