Trivia: When Detective Arbogast gets attacked by Norman's mother and falls backwards down the stairs, the actor, Martin Balsam, was actually just tap-dancing in front of a blue/green screen.
Suggested correction: This is partially correct. The actor is in front of a screen projecting the image of the stairs behind him, not blue or green screened onto the image. In addition, according to at least one analysis going into detail of the making of the film, he was sitting on a slanted chair, so he was convincingly horizontal and flailing his arms only, not "tap dancing."
Plot hole: When the cop comes back after making the phone call, he's just missed Norman. He heads over to the office and calls out for Bates. He's in there around 45 seconds. Then he leaves and heads towards the big house. How can Norman be at the house ready to kill him in his mothers clothes, when he had no idea the cop was back and he would not have had time to get there from where he was, right at the far end of the cabins?
Suggested correction: Because Norman heard/saw him coming up the road. Norman hesitates before he goes into a cabin or behind one, it's not clear which. He has seen Arbogast's car before and recognizes it. He goes the back way between the two buildings of cabins (just like Vera miles does later when she goes to the house) and up to the house to put the dress/wig on and be ready for Arbogast when he gets to the top of the stairs.
Continuity mistake: When Arbogast reaches the top of the stairs, Mother Bates stabs him in the chest; but when the camera angle changes, the wound is on his face.
Suggested correction: That's blood splatter, not the wound.