Continuity mistake: After Pongo spots Anita and Perdita walking towards the park, Pongo moves the time forward on the clock and he leaves the dial's hinged bezel open as he rushes to the door and barks, but when Roger checks the time on the clock the bezel is closed. (00:06:20)
Continuity mistake: When Elizabeth Medina starts to open her coffin you see her hand reach out and grab the side edge but in the next shot her hand is gone.
Other mistake: When the parent monster is just about to enter Piccadilly square, for a brief moment a view of a bus is shown. The writing on the bus is reversed.
Continuity mistake: Doris picks up the phone and there's a cutaway shot on Johnny playing his guitar as he listens. The stockings Doris tossed at him are gone from the guitar head, but they are back when the phone call is over. (00:05:10)
Continuity mistake: Chet visits his friends that are playing poker. He falls asleep and wakes when he hears the news on the radio. The band aids on his wound change abruptly position in close-up. (00:12:10)
Factual error: At the conclusion, the island gets blown apart by a volcanic eruption while the children and the hospital staff watch from aboard a schooner off the coast. A volcanic explosion of this magnitude would have created pyroclastic surges that would overtake the boat, killing everyone aboard. (During the 1883 eruption of Krakatoa a pyroclastic surge stretched 30 miles to the coast of Sumatra, killing residents of some villages along that coast before the explosion that triggered the devastating tsunami (which killed over 30,000 people).