The Postman Always Rings Twice (1946)

Revealing mistake: When John Garfield is trying to stop Lana Turner from calling the District Attorney, Garfield holds the receiver up in the air off the hook. Then the phone rings. But a phone cannot ring when it is off the hook.

Continuity mistake: When Frank, the DA and the policeman are discussing the accident, the policeman notices the electrocuted cat and it is shown next to the ladder. In the subsequent wide shot the cat is lying between the beams of the ladder. (00:42:50 - 00:43:35)

jle

Continuity mistake: When Nick arrives home, drunk, from L.A. the package he is carrying is fully wrapped in paper and he is not smoking. When he comes in the front door, the package is half unwrapped with the towels hanging out and he has a cigarette in his mouth. (00:26:00)

jle

Cora Smith: It's too bad Nick took the car.
Frank Chambers: Even if it was here we couldn't take it, unless we'd want to spend the night in jail. Stealing a man's wife, that's nothing, but stealing a man's car, that's larceny.

Cora Smith: That note I left Nick, if he gets back before we do and finds it.
Frank Chambers: Where'd you leave it?
Cora Smith: In the cash register.
Frank Chambers: That's terrific, that's the first place he'll look.

Frank Chambers: You know, there's something about this that's like, well it's like you're expecting a letter that you're just crazy to get, and you're hanging around the front door for fear you might not hear him ring. You never realise that he always rings twice.