When Rita is walking to after from the accident the cut on the right side of her head disappears and reappears. Also, even though the blood is obviously dry, the blood pattern is completely different each time.
The golf club is missing from Adam's Boxster when he is on the phone and driving home. It reappears as he arrives at his driveway.
When the Castigliane brothers enter the room and sit down at the table (at 0:28), Vincenzo Castigliane (Dan Hedaya) opens the briefcase, takes out an envelope and slides it across the table to Mr. Darby. The opening of the envelope is on the upper side, but when it arrives to Mr. Darby, he turns it to open it, so the opening is on the bottom side.
Director Adam Kesher's frenzied attack on the Castigliane brother's limousine immediately scatters pigeons in the far distance, but only when he finally knocks out a headlight (a relatively minor impact) do the pigeons directly behind the car fly up.
When Betty arrives at LA she is walking out from the top level of LAX. Arrivals are at the bottom level, Departures are at the top.
When the camera dollies back from the five vocalists in the recording booth, the two VU (volume unit) meters on the control panel are at zero level indicating that no sound is being recorded or heard on the engineer's headphones. However, this may not be a mistake, as the singers are lip-syncing with an existing recording, and the scene is only being filmed for audition purposes.
When Betty and Rita are rehearsing for Betty's audition, Rita can be seen reading from a script with lines for "Betty" and "Rita." However, due to the dream logic of the film, this may be interpreted as a clue to what is really going on.
At the moment of impact in the opening car crash, an explosion reveals that the white car is devoid of its three joyriding occupants.
During the long tracking shot of the mob goon (Kenny) entering the director's house, a crew member is reflected in the window.
When Adam Kesher leaves the meeting to smash the limo's windows, the crew is reflected in the window across the street, pushing the cameraman and dolly.
In the shot of the dark colored car with the two men in suits driving by the apartment complex right before Betty Elms leaves for her audition (1:13:23), for a moment the top of the camera is reflected in the bottom part of the car's rear window.
When Betty enters her Aunt's apartment for the first time, she leaves her suitcase out in the courtyard, and never goes back for it.
When the detectives talk about finding the gun in the back of the limo, they call the limo a "Caddy" when in fact the limo is actually a late 1980's Lincoln Town Car Stretch Limo.
The Sony-brand telephone that Betty and Rita use to call Diane Selwyn has separate buttons for 'on' and 'off' functions. However, Betty presses the 'on' button to turn the phone off following the call.