Revealing mistake: In the opening scene where the zombie kills Johnny. When they fall against the tombstone you can tell it is a dummy.
Continuity mistake: After Barry has jumped into the water reclaim the crown, he comes out of the water with a perfectly clean shirt, but in the next shot the blood is back on his shirt as expected. (00:22:50)
Continuity mistake: When the old car blows up both of the dead zombies are gone. (00:21:40)
Revealing mistake: When the chair moves across the kitchen floor, Craig T. Nelson goes to investigate it (after it has stopped moving). He goes up to the chair and flips it over. If you look closely, Craig almost hits the camera with the chair's legs. You can tell this has happened because the camera moves up very quickly and Craig looks straight at the camera crew with very big guilty eyes. This is more easily visible on the widescreen version of the film. (00:33:30)
Factual error: When they're first entering the whaling camp, a penguin startles Miller. That penguin was a black-footed penguin, which is a bird native to much warmer climates. If that little guy had actually been in Antarctica, he would have died within minutes. (00:20:40)
Plot hole: Det. Kerry says at the scene of Paul's trap, "He had two hours." There is no way she could have known that. The clock simply said 3:00 and the tape specifically says "you have until 3 o'clock or this room will become your tomb". No way to know that's two hours after the fact. (00:17:30)
Continuity mistake: When Bucky jumps on the hood of the bus to get back in, the Creeper flies from in front of the moon towards the bus causing all the kids to run away. Bucky can still be seen staying put on the hood when they run - however in the next shot of all the kids running you see him at the front of the pack which would have not been possible given that he didn't run right away.
Factual error: At the end when Ben Willis and his son have Julie at the graves, Ray shows up with a gun. He fires at Ben but there is no bullet in the chamber. Later after the fight between Ray and Ben's son Julie picks up the six-shot gun and fires 8 shots at Ben.
Visible crew/equipment: There's a scene in which someone goes into a phone booth to make a call. As the phone booth door closes you can see a reflection of the cameraman.
Continuity mistake: When Constantine manages to get the mirror through the window he falls on his back. To the right on the screen a chair lies on the floor beside a dresser. A few shots later when it cuts to Constantine getting up we can see the chair has changed position as its back now covers the opening of the dresser. (00:08:15)
Visible crew/equipment: If you look really close in the background as the killer throws Cici off the balcony, you can see someone sitting in a tree, wearing black, with a camera. (00:33:35)
Factual error: When Janet Leigh is shown lying dead on the floor of the shower, there is a close-up of her open eye. The pupil is contracted to a pinpoint (obviously due to the bright lighting) where it should have been dilated. After the film was released, Hitchcock heard from several ophthalmologists who pointed this out and suggested he use belladonna eye drops in the eyes of "dead" people in future films, as the chemical prevents the pupils from contracting. (00:48:30)
Revealing mistake: When the lawn mower the heroes send off as a diversion crashes you can see a wire pulling it. (01:01:30)
Continuity mistake: When Kelly is on the boat with Hank and the soon to be headless deputy, her green vest (life-jacket) is fully unzipped. When we see her immediately after she's been knocked in the water, her jacket is zipped almost all the way up.