Deliberate mistake: When Eliza is about to be bathed, the mirror keeps turning around between shots to avoid reflecting the filming crew.
Continuity mistake: When Dr. Morrissey comes to George and Judy's house on Sunday night after the fishing trip to bring them some fish, he sits down on the couch and removes his glasses. Then, in the next shot, his glasses are back on again. He wouldn't have had time to put his glasses back on. (01:09:45)
Continuity mistake: Ann Margaret is seen dancing with high heeled shoes at the beginning of a dance routine and during the routine is seen in flat ballet shoes, then near the end she is seen wearing high heeled shoes again.
Revealing mistake: When Marnie is dreaming, watch her window. The curtains move as if there is wind, but the window is closed.
Visible crew/equipment: In the beginning, when Dino is stopped by the police, the stage lights are reflected on his sun glasses.
Continuity mistake: At Molly's party after returning from Europe, the Duchess is introduced, and everyone bows. The shot shows Molly reaching for her neighbor who's standing straight, to bow down, and she does. Then there is a long shot showing the crowd, and the neighbor is again standing, and then you see Molly reach out for her again as she just had.
Continuity mistake: When the initial site team comes to the Tatum's, the second jeep in the convoy has the same supposedly unique serial number as the one the general arrives in a week later.
Continuity mistake: When Shirley Maclaine goes swimming in the blue lagoon, her hair is all wet before she enters the cave, but once in the cave her hair is only wet on the ends.
Factual error: The radio Walter uses on the island has no apparent power source; we never see either batteries or a hand-cranked generator.
Visible crew/equipment: The shadow of a camera and cameraman are revealed on the left side while the President (Frederic March) is moving from one room to another (door jamb), after learning about Martin Balsam's death. (01:20:00 - 01:21:00)