The play which the film is based on is done in three acts; act one is the final dress rehearsal; act two is the matinee performance; act three is the evening performance. The bridge scenes, with Michael Caine's voiceover narration, including the opening scene where he leaves the theatre and the ending scene where he returns, were written for the film and do not appear in the play. In the play, the last line is the frantic call for "Curtain!"
The original Broadway production of "Noises Off" by Michael Frayn opened on December 11, 1983 at the Brooks Atkinson Theater running for 553 performances with a cast that included Victor Garber and Dorothy Loudon and received a nomination for the 1984 Tony Award for Best Play.
Two of the characters names are changed from the original stage play: Lloyd Dallas (the director) and Frederick Fellows (the actor). In the movie version they are Lloyd Fellows (the director) and Frederick Dallas (the actor).
Lloyd's speech/rant to Tim before the matinee about the problems he's having directing Hamlet was changed from the play. In the play, Lloyd is directing a production of Richard III, and all the characters/references reflect that. It was changed in the movie because it was felt that Hamlet would be better-known to American audiences.