Based on

Movies like Three Hams on Rye (1950)

The stooges are stage hands who also have small parts in a big play. They quickly get on the bad side of the producer. First they fail to prevent a famous critic from sneaking into the audience. Then Shemp accidentally adds a pot holder into a cake they bake as a prop. During the play the stooges (as southern gentlemen) and the rest of the cast spit up feathers during what was supposed to be a serious scene. The critic thinks it's a hilarious satire and the boys are redeemed.