Factual error: At the end when the shark is attacking the boat and the electronic device is used you can hear the shark roar. Sharks cannot produce this sound since they have no vocal cords.
Factual error: The heat from Dutch's body would warm the mud up in a matter of seconds (tested by the Mythbusters). It doesn't even cover all of his skin or his eyes. And the Predator isn't filtering his input for only large heat sources. His normal vision tracks in on a rat hiding just above Dutch.
Factual error: The opening sequence is set in the 1950s, but there are modern school buses, cars, TV aerials, traffic signs, clothes, house architecture and style.
Factual error: In the "Groovy" shed scene, Ash holds a double-barreled shotgun in one hand and saws through the gun barrels with his newly-mounted chainsaw in about 2 seconds flat. He could no more cut through a hardened steel shotgun barrel with a chainsaw than he could cut through a marble counter-top with a butter knife.
Factual error: Sam neglects to cock his gun before he shoots Old Cheif Woodenhead. (00:24:40)
Factual error: This film begins with a foreboding quote attributed to Edgar Allen Poe: "Sleep. Those little slices of death. How I loathe them." Problem is, Poe never wrote any such thing (and neither did Henry Wadsworth Longfellow), despite decades of misquotes and misattributions across the Internet. So, where did the quote actually originate? The answer is Walter Reisch, lead screenwriter on the 1959 film "Journey to the Center of the Earth." In Reisch's screenplay, the antagonist Count Arne Saknussemm is urged to get some rest, to which he memorably replies, "I don't sleep. I hate those little slices of death."
Factual error: Horace was not holding the shotgun properly - the kickback would have not only made him miss Gillman, but it would have knocked Horace to the ground.
Factual error: In the movie's opening scene, it's night and we see the full moon. There's an elderly priest lying in bed. The next morning we learn the priest has suffered a stroke and been taken to the hospital. That day, Prof. Birack pauses before entering a campus building to look toward the sun. We see a thin crescent moon near the sun, as if there will be an eclipse in the next few days. That night, Brian is waiting outside a campus building for Catherine to come out. He looks up at the full moon. In following days, other characters see the daytime crescent moon, still approaching the sun. It's impossible to see the full moon at night AND a crescent moon during the day in that brief a time span. It would be more like 12-14 days for the lunar phase cycle to progress from one to the other (much less back again).