About 45 minutes into the film, Margo and Bill are having an argument about Eve before his birthday party. Margo angrily folds her arms across her chest and her diamond bracelet clasp breaks and dangles against her dress. It isn't part of the story. It is fixed in the next frame.
In the closing credits, the character of Bill Sampson is shown as Bill Simpson.
After she drinks the martinis, Margo goes up the stairs holding the cigarette in her right hand. Next shot it is in her left hand.
In The Cub Room, Margo holds a lit cigarette. In the next shot, without having put it in her mouth, she puffs a cloud of smoke.
After Bill proposes a toast to Margo, she changes the cigarette from her left hand to her right, but in the next shot it is still in her left hand.
When Addison slaps Eve in the hotel room, her head snaps toward him rather than away, indicating a "stage" slap.
When the car runs out of gas, the fuel gauge still shows that the tank is just under half full.
When Karen, Bill and Margo are returning from a long weekend in the country, they run out of gas. They mention having driven the car over the last few days, but in the two closeups of the dashboard the odometer only reads between 00023 and 00024 miles - the studio probably bought a new car and cut it apart for the interior process shots.
When Eve and Addison DeWitt are walking down the street in New Haven from the Shubert Theatre, the pedestrians behind them are walking at a faster pace, but never gain any ground on them. This is because "back projection" is being used; George Sanders and Anne Baxter are not really walking down a street. They are "walking in place" and the background is actually projected film being shown behind them.
In the car, the snow tracks seen through the back window behind Karen curve to the left, whilst those behind Margo curve to the right.
When they turn the car radio on the music starts immediately. But before the age of solid-state electronics the vacuum tubes used in radios at that time needed to warm up before you could hear anything. This occurs twice.
When the protagonists are sitting at their table in the Cub Room scene, a waiter is seen walking toward their table, but when the angle changes, an inordinate amount of time elapses before he actually passes the table.
When Addison and Eve are together in the Cub Room, he taps his cigarette holder to knock the ash off the cigarette, which falls out of the holder into the ashtray. He doesn't notice while he speaks, and keeps tapping the empty holder.
After Margo reads the note written by Eve, Bill says, "I understand she's now the understudy in there." However, when he turns his head to the camera, his lips aren't forming any words.
While Phoebe is looking at herself in the mirror during the final scene, a crew member sitting on a crane is visible for a few seconds at the top of the shot.
At right about 51:58 into the movie, when Margo and Lloyd are talking in the kitchen, right after Margo says "Cora...still a girl of twenty", the camera that is filming the scene shakes as if it was accidentally bumped.
A boom mike shadow can be seen just before the 92m mark, when Addison and Karen are talking to Eve in the foyer of the "21" restaurant.
When Margo calls Bill for his birthday, she is in New York and he is in L.A. Her clock says 3:00 and his says 11:00. But there is only a three-hour difference between New York and L.A.
It's not clear how Karen would've drained a car's almost-full gas tank of gas. There's no drain plug under a car to drain it of gas. The only way would be to siphon it out of the filler tube at the top. It wouldn't be an easy task for a society lady, and it would take a long time. It can be a messy business so if she did do it she would probably stink of gas.
In the Cub room, after Eve has returned from her restroom talk with Karen, Addison DeWitt is tapping his cigarette into the ashtray. The cigarette falls off from the holder. He continues tapping until he realizes it fell off and then he attempts to hide the holder behind his hands.
The hands in the bedside clocks do not move.
At the beginning of Addison DeWitt's "introduction-speech" of everyone in the movie, he's supposed to look at the stage, but the rest of the audience behind him is clearly staring in a different direction.
When Eve tells her life story in the dressing room, she says "then the war came, and we got married. Eddie was in the air force - and they sent him to the South Pacific." The "Air Force" wasn't formed until after the war in 1947. During the war it was called the Army Air Corps.