Character mistake: In the scenes in San Diego, all the scenes outside the sub are taking place during daylight hours. Immediately after the crewman relays the message about the mysterious telegraph transmission, the scene shifts to the sub. The commander asks what time it is in Melbourne and is told it is 1500 hours (3PM). But if it were that time in Melbourne, it would be 10PM in San Diego, and thus not during daylight hours. (01:33:30 - 01:38:05)
Continuity mistake: After the boy's Noel-Coward-lookalike father says, 'Et les fruits?', goes into the kitchen, and disappears out of shot, watch the cat on top of the bookcase to the left of the door. Before the boy runs into shot, the cat suddenly changes position and a mysterious lens flare appears on the right of the screen, showing that it's actually two shots edited together.
Continuity mistake: The escape train stops at a station at which another train has been the site of a massacre. One of the victims of this massacre has his head leaning out of a railway carriage window. As Kenneth More and Lauren Bacall from the escape train walk about the station, he can be seen raising and then lowering his head again as he realises that the 'take' is not complete.
Plot hole: When the Allies blow up the airfield they pour gunfire from the backs of the trucks into the tents where the Japanese soldiers are eating. If you watch carefully you will see that the Allied guys in the truck nearest the screen are pouring lead through their comrades in the other truck. Another classic case of 'friendly fire'.
Continuity mistake: The background shots of the Matterhorn show it with a clear sky, then a cloud around it, then a clear sky again. This keeps happening.
Other mistake: When Anne and Peter are looking at the stars, Anne points to a star and Peter knows what star she's pointing to. It is impossible to point to a star and have someone else know exactly what star you're pointing to. Try it.
Other mistake: When the Behemoth swims up the river & capsizes the ferry, a static model is used that bears no resemblance to the animation model seen throughout the film.
Other mistake: A police officer fires two shots, hitting a bank robber in the back. The "bullets" do not make holes in the robber's coat. All they do is create two tiny puffs of dust.
Continuity mistake: Susie, a six-year-old girl, leans over a bathtub and reaches for a rubber duck. She falls into the tub but it obvious the tub has no water. (The actress, Terry Burnham, landed on a pad or cushion.) Immediately after she falls, there is a very noticeable jump in the film. Then water splashes up but the splash is much too high to have been made by the little girl. The next scene shows the mother entering the bathroom and the little girl, now completely drenched, standing up in the bathtub.