The Boy Friend

When the leading lady of a low-budget musical revue sprains her ankle, the assistant stage manager is forced to understudy and perform in her place, becoming a star and finding love in the process.
The assistant stage manager of a small-time theatrical company is forced to understudy for the leading lady at a matinée performance at which an illustrious Hollywood director is in the audience scouting for actors to be in his latest "all-talking, all-dancing, all-singing" extravaganza.