Revealing mistake: As Roney opens a drawer in a filing cabinet, a blue case and a wallet folder appear on top of the cabinet, that were not there in a previous shot. (00:21:25)
Revealing mistake: When Quatermass and Breen are theorising inside the spaceship. Breen says "What do you mean by that?" His face has beads of sweat on it, in the next shot his face is dry. (00:39:15)
Revealing mistake: When Roney enters the spaceship, just before he first helps Quatermass to remove the insects from the their chamber, he is wearing gloves. Then in a shot from inside the hull of the ship, he is not wearing a glove on his left hand. When he reappears outside, he is wearing gloves. (00:39:56)
Revealing mistake: The flashlight that the drillman used when the lights went out around the spaceship didn't match the light from the spot used by the film crew.
Revealing mistake: A skeleton of early man is found by a workman digging through mud at an extension to the Underground railway system in London. The skeleton is suspended in a pocket of air, however, and shows no mud inside the rib cage or other body cavities.
Revealing mistake: After the spaceship becomes alive and causes a cave-in, Barbara easily stumbles and moves the large chunks of broken cement beams as she leaves the pit with Quatermass.
