Continuity: The size of the sandwich Danny was eating at the beginning of the movie.
Continuity: When Jack and Danny are sitting on the bed and talking, the position of Jack's left hand in the camera keeps changing, sometimes the hand is behind him, and sometimes it is on Danny's shoulder.
When Wendy was talking to Danny on the bed, it was obvious that there was a bug crawling down from the camera lens.
Continuity: Wendy's hand when Jack is talking about his nightmare.
The equipment can be seen: when the film begins, following the tour group when they first walked into the apartment, the shadow of the camera can be seen on Wendy and Jack.
Continuity: When Wendy went to see Jack to see what he was writing, Jack yelled at her angrily and tore the manuscript paper from the typewriter. But when Wendy left the room, a brand-new manuscript paper was lying on the typewriter.
Continuity: When Wendy knocked Jack stunned with a baseball bat, his feet were wearing white soft-soled sneakers; but when he was dragged to the pantry, the shoes on his feet had changed to beach-colored shoes. Walking shoes.
Heuristic error: When Wendy and Danny are watching TV, the TV is neither plugged in nor connected to the antenna.
The crew and props: At the beginning of the film, the shadow of the helicopter is projected on the lower right corner of the screen.
An anachronism: The name of the song played in the ballroom scene is "Midnight, the Stars, and You". This song didn't appear until 1932, and the film's story took place in 1921.
