Continuity mistake: When Dr Sobel is eating a dish of spaghetti in the restaurant, there is a dish of plain lasagna in the foreground. When Paul Viti's cousin arrives and the camera pulls back, the lasagna has melted cheese on top.
Factual error: When young Vitti and young Manetta hijacked the farmer off his tractor, a John Deere 730, they pulled the hand clutch backward to go and pushed it forward to stop. On these tractors, the hand clutch operation is just the opposite. Additionally, the JD 730 was not produced until 1958. The mob meeting was in 1957.
Continuity mistake: In the big shootout at the end in the car park the huge machine gun fires into the warehouse leaving some bullet holes in the large corrugated door. In the next, wide shot of all the families running around in the warehouse the bullet holes are gone.