Continuity mistake: In the park, when Pongo tries to get Roger to meet Anita he yanks Roger ahead, and Roger leaves his hat on the bench. In the next shot, when Roger and Anita are entwined in Pongo's leash, Roger is wearing his hat. (00:09:30)
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: 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)
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)
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).