Continuity mistake: At one point, the gigantic title character knocks over a city bus. For a moment, the word TONKA can be seen on the underside of the vehicle.
Visible crew/equipment: During the "How Long Has This Been Going On" number, Hepburn dances by a mirror - reflected in it are the camera crew, desperately trying to get out of the image.
Deliberate mistake: At the beginning of the movie Mr. Coates tells his wife that he will be gone "all of three months, maybe four." The first time we see Bud and Elizabeth Searcy she tells Travis that her dog is pregnant and that Old Yeller is the father. We then see her dog that does not look very pregnant. The next time we see Elizabeth she presents Travis with one of the pups. The problem is that the pup that was supposedly just born is about 4 months old.
Revealing mistake: Allison is wounded by a grenade fragment while disabling the Japanese 105's. But when his bloody shoulder is first seen, the blood stain is visibly too bright for real blood.
Revealing mistake: An open water shot of the Constitution shows the wake from the camera boat.
Continuity mistake: When the group go out to inspect the house damaged by the monoliths, the dirt around the rocks is white while the rest is dark. The professor squats down and picks up white dirt in his left hand and dark dirt in his right hand, then calls the geologist. In a close up, he opens his hands and the dirt colors have changed hands - the shot has been reversed.
Continuity mistake: At the start of the film when Tom is doing his trial run, he is forced off the road to avoid crashing into two oncoming trucks, driven by Johnny and Red. His truck has the number thirteen number board on the front, which isn't on it during any other time during the trial run, although it's on the truck for the rest of the film.
Plot hole: If Ashley kisses somebody, her good luck is passed on to them. However, Ashley kisses Chris Hemmington before she kisses Jake, so shouldn't Chris Hemmington have her luck?
Factual error: When the UBoat changes course, Andrews, operating the radar repeater, is immediately able to provide the bridge with the target's new course and speed. This would be impossible without extensive calculations and at least range and bearing plots once the target has steadied up on the new course, either figured on the scope screen or on a maneuvering board. One must remember that both vessels' courses and speeds must be taken into account when making computations, and the relative direction of a target's travel most often is not its true course.
Factual error: As the movie opens, the submarine is dispatching frogmen to acquire Japanese mines that are sonar-proof. The problem with this is that in order to locate mines by sonar, either the mines must make noises to be picked up by passive hydrophones, or the submarine has to start pinging with active sonar. Doing this makes the submarine vulnerable to any enemy listening in. I can't imagine a submarine venturing into a mined strait, announcing to one and all, "Here I am"..
Continuity mistake: During the slow-motion sequence, Speedy slams the mallet on the cat's paw and leaves the mallet on the ground when he rescues the mouse. When he puts a stick of dynamite on the cat's tongue, the mallet has gone.