The cars parked on the street as seen from inside Marion's car do not match the cars as seen from outside.
When Norman is mopping the bathroom, the mop goes from bloody pink to unbloodied between shots, without rinsing.
As Marion waits at a traffic light in downtown Phoenix, a lady carrying a package tied with red ribbon (string in Psycho (1960)) followed by a man with a jacket over his left arm cross the street directly in front of Marion's car as Lowry and Cassidy enter the frame on the left. Unlike the 1960 film, after Lowry and Cassidy have passed by Marion's car left-to-right, the same lady with the package and man with the jacket are seen crossing from the right again.
When the stabbed Marion Crane leans against the wall, she leaves a horizontal blood print on the tiles. All the wounds on her back are vertical.
When Lila first meets Sam in the hardware store, the flap on his left pocket moves between being tucked in the pocket and not. And once Arbogast enters the scene, a pen suddenly appears in the same pocket even tho Sam had not had a pen in his hand or pocket when he came out to meet Lila from the back room where he had been writing the letter to Marion.
When Norman has moved Marion's car closer to the door to her room he unlocks the trunk with a key. Unless broken, the lock to the trunk on a Volvo 740 is unlocked via central locking.
Even though modern cinema allowed for a gorier depiction of Marion's stabbing, at no time does any shot of the butcher knife have blood on it.
In the original version many viewers noted that close-ups of the dead Marion's eyes showed no dilation as she lay on the floor. Van Zandt chose not to show Marion with dilated eyes either, even though a CGI closeup of an eye dilating was inserted moments earlier as Marion sinks in the tub.
The $4,036.00 that Norma Crane has written on a slip of paper represents an incorrect amount. At the time the movie was shot the CA state minimum sales tax was 6%. Based on the $4,000 paid to the dealer for new car, the tax would have been at least $240.00 (total amount= $4240.00, not $4036.00).
When Bates is rolling Marion's car into the lake, the taillights are filled with water from previous takes.
The opening scene is supposed to be 2:48 in the afternoon, but it's quite obvious that it was filmed at sunrise, probably on a Saturday or Sunday morning. There is no street activity, and the light from the right (east) is very weak and nearly horizontal. If it had been shot in mid-afternoon the sun would have been higher, the light stronger, and shadows pronounced and angled.
Just as Arbogast is approaching the top of the stair flight in Norman's house, a high-angle shot clearly shows Arbogast's head swivel in the direction of Norman's mother who is at the same time rushing out of her bedroom door with a knife in her hand, but he reacts as if he hasn't seen her at all, neither getting alarmed nor taking any evasive measure, and continues to climb up the stairs nonchalantly.
Since $1,000 bills are not used by the public for general circulation, the 2 bundles representing $400,000 stolen by Marion are far too small in size.
The bundles of money Marion Crane has are of $1,000 bills (as clearly seen in one shot) when in actuality circulation of bills larger than $100 were halted by President Richard Nixon in 1969.
There are several conflicting design motifs throughout the film: all of the cars are contemporary to the films production era, but Marion's car is an 80s Volvo, Sam's truck is from the early 1950s, Lila's Walkman is from the 80s, and the design of the motel is late 60s, but the toilets are 1940s design.
The helicopter carrying the camera is visible on the mirrored windows of the first building in the opening shot.
As Lila descends the stairwell leading to the basement, all of the walls and decor around her are the muted colors and antique designs true to the Bates' turn-of-the-century house, but when she opens the door into the basement, large translucent studio lights can plainly be seen behind her.
During the sinking of Marion's car in the swamp, the moment it hits the hidden hydraulic lift, a distinct thud can be heard, as well as the leveling out of the car as it adjusts to the flat surface. Hitchcock was savvy enough to make sure that this sound would not be heard by 1960s audiences.
When Sam first meets Lila in the hardware store, he tells character Flea, "Bob ... run out and get some lunch." The name tag sewn onto Bob's work shirt clearly says "Rick"
Arbogast's line stating he will return in an hour or less was shortened, removing the "or less" piece, yet Lila still quotes him as saying "an hour or less" after the phone call.
When Marion subtracted the $4,036.00 cost of her "new" car from $400,000, she made a $1.00 error and wrote $395,963.00.