Amadeus (1984)

Visible crew/equipment: When Mozart and family visit a parody on several operas of his in a public theater, in one part of the show little people appear from all sides of the stage. When the last of the little people (carrying a model of horse) hops through a paper wall on the side of the stage, you can see a man in jeans walking behind the set.

Emanuel Schikaneder: Look, I asked you if we could start rehearsals next week and you said yes.
Wolfgang Amadeus Mozart: Well, we can.
Emanuel Schikaneder: So let me see it. Where is it?
Wolfgang Amadeus Mozart: Here. It's all right here in my noodle. The rest is just scribbling. Scribbling and bibbling, bibbling and scribbling.

Trivia: The actors in the film are never actually heard playing the keyboard instruments. The actors played the keyboards in time to recorded music being played on set or via earphone. However, in order to avoid mistake watchers noticing it, the actors had to learn the pieces, so that they are almost always playing the right keys for the music.