Visible crew/equipment: In the officer Krupke song, set lights are visible on the stairs to the audience left and right.
Continuity mistake: When one of the Jets jumps on the pickup to unload all the veggies and watermelons, the car on the left changes between shots. Also, when he is about to unload the veggies, the pick-up is approaching a blue squared van on the left. The shot changes, and the van is further away.
Factual error: At the beginning of Quintet, a modern Manhattan skyline is visible in the distance not a late 1950s skyline. Also, the view is consistent with the Paterson, NJ filming location, not the Upper West Side.
Factual error: Suspended traffic lights didn't exist in fifties NYC.