During the robbery, it's clear that a significant amount of the money is in neatly banded bundles of crisp brand-new bills, yet when it's transferred from the duffel bag to the suitcase, all the bills are loose, unstacked, and appear well-used.
In the opening sequence, both the narrator and the track announcer refer to the "fifth" race. But the bet tickets that Marvin Unger has say "sixth race." The subtitles say both 5th and 6th for different references.
When Marvin Unger jots down the time and place of the gang's meeting on his betting ticket in the first scene at the racetrack, he misspells the abbreviation for "apartment" as "APP." But when the ticket is shown in close-up (as Marvin slips it over the counter to George, the cashier) it reads correctly: "APT."
During the fight scene at the race track where the robber is let in the door in two scenes viewed from different angles, it's clear that the door is opened in different ways, and also that the robber is much quicker the second time, even though the scene is supposed to be the same.
When the parking lot attendant hands Nikki a horseshoe, he holds the curved part in one shot and the end in the next.
When George shoots Sherry, kills her, he fires his gun pointing mostly upward, yet it hits her around the stomach area, where she clutches before saying her last words and falling.
When Sherry is lying on the bed, knocked unconscious after she was discovered eavesdropping on the robbers, her eyelids are seen to blink slightly. However, she was feigning being unconscious which is how she knew to repeat her husband's fake story about her suspecting him of having an affair.
The bird in the cage (after George has shot Shelley and is about to fall down) is obviously stuffed. In the next shot on the ground, it's a live bird.
When Peatty fixes his wife a drink, the studio above where the ceiling of the set ends can be seen briefly.
When Sherry is shot, the bullet hits her in the middle of her torso, but George's angle with the gun would have missed her entirely. The shot would have hit the ceiling.
The flower box that Mike the bartender takes out of the bus station locker is considerably shorter than the box he carries into the racetrack locker room.
On the inside of the door at Johnny's hideout it is written in chalk: 78 x 29. This refers to the door measurements 78" x 29", obviously written on the door by the construction department and not removed before filming.
When George starts shooting his gun from the doorway, he's pointing it directly toward George standing across from him. Val manages to fire his shotgun once, hitting George. Everyone is standing outside the line of fire yet somehow the entire room is killed by only a few gunshots pointed away from them.
When George is forcibly being removed from the apartment he says, "No, I'm not leaving Sherry." but his lips/mouth don't move...obviously dubbed in.
At the motel, the camera shadow along with the crane and operator can be seen on the pavement.
When Sherry is removing her makeup in their room, George is moving toward her. When he hits his mark, announcing that he is dropping out, the shadow of a crew member's head is clearly seen on his shirt and then fades on the right side.
When three members of the gang hear that someone is coming in and turn around, expecting him to be Johnny with the money, the shadow of the mic and of the camera becomes visible.
Every time Johnny Clay pulls up to the hotel, the shadow of the boom mic is visible on the road.
When climbing and descending the spiral stairs outside the cash room, Johnny leaves a number of fingerprints on the railing and central pillar - an unlikely mistake for a seasoned criminal.
When Patty gets out his gun in the staff cloakroom, he cocks it first and then puts in the magazine. You have to cock it after putting the magazine in, in order to advance the first bullet into the chamber. Presumably, he does this later.