Joseph Papp's notion of staging one of Gilbert and Sullivan's best-loved operettas with two pop singers (Linda Ronstadt and Rex Smith) in the leads paid off as a surprise Broadway smash in the early 1980s, and this film faithfully reproduces Papp's production, featuring most of the original cast and the original director. Frederic (Smith) has been taught since childhood to be a sea-going bandit by the Pirate King (Kevin Kline), but with his 21st birthday imminent, Frederic wants to leave pirating behind, especially after he becomes infatuated with innocent Mabel (Ronstadt). But the Pirate King informs Frederic that since he was born on the last day of February on a Leap Year, his 21st birthday won't roll around for some time yet, and he still owes the King some raiding on the high seas. To Frederic's embarrassment, the Pirate King's next target turns out to be Major General Stanley (George Rose), Mabel's father! The Pirates of Penzance also features Angela Lansbury as Ruth (the sole major casting change from the Broadway production -- Estelle Parsons played the role on stage).
by Mark Deming synopsis