In Act II, there is an extra song ("My Eyes Are Fully Open") that is not originally from "The Pirates of Penzance." It's a modified version of a song from William S. Gilbert and Arthur Sullivan's "Ruddigore". The inclusion of this song required Kevin Kline, Angela Lansbury, and Rex Smith to sing one of most dizzyingly rapid songs in the entire Gilbert and Sullivan catalog.
The Broadway production of "The Pirates of Penzance" by William S. Gilbert and Arthur Sullivan opened at the Uris Theater in New York on January 8, 1981 and ran for 787 performances. The musical received four Tony Award nominations for acting including George Rose and Tony Azito who both recreated their roles in the movie version.
The film's failure at the box office had nothing to do with the reviews, which were often quite positive. The real problem lay with Universal's decision to release the film simultaneously to SelectTV and to theaters. Theater owners were so angry that they boycotted the film; in the end, a grand total of 92 theaters agreed to show it, and it enjoyed a long run at only one of them (in Washington, DC, where it became a cult success and played several weeks).
Estelle Parsons was the only member of the principal cast of the 1982 Broadway production (Kline, Smith, Rondstadt, Azito, Rose, Parsons) not to appear in the film. She was replaced with Angela Lansbury for Ruth.
Sir Arthur Sullivan's original orchestrations, nearly always used in stage revivals of all of Gilbert and Sullivan's operettas, as well as in the 1939 and 1967 film versions of "The Mikado", were completely discarded and rewritten for the 1982 revival of "The Pirates of Penzance" and this film version of it.
Pirates of Penzance was shown on a Los Angeles television movies channel - SelecTV - simultaneously with its theatrical release. This was only the second time that something like this had been tried - in 1956, Laurence Olivier's 1955 film version of Shakespeare's "Richard III" had its U.S. premiere in New York City and its television premiere on NBC on the same day. Like "The Pirates of Penzance", "Richard III" was also a box office flop, but unlike the former film, "Richard III" won universal acclaim from the critics, became a film classic, and was not boycotted during its theatrical run.