Factual error: If the Russian cosmonauts need special suits to survive out in space, so should Lacy when she is abducted by Nuclear Man. (00:02:50 - 01:20:20)
Factual error: Hot Air Balloon's have no lateral control. They fly in the direction the wind is blowing, so it's rather impossible for two hot air balloon's very close to each other to be flying in different directions, let alone fly exactly to the desired locations.
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: The Joes chase Cobra into the snowy mountains and attack inside the weird cave. One of the Joe's vehicles splits to a driving section, and Road Block flying up in a little fighter. Road Block is holding a large rifle with both hands, yet the fighter goes up and turns around and begins flying at his control but he never touches a steering wheel or anything. Just his big gun. And he does not speak so no voice commands are given. How is he flying with no hands? (00:19:40)
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).