In the FMV where Sephiroth kills Aerith; when his sword goes through her, in the close-up the brown belt that she wears around her waist has disappeared. In every other shot she is wearing it.
The fans on the gondola that takes the party to the Gold Saucer switch from the back of the vehicle to the front during the FMV sequence when it leaves the station.
The giant cannon is visibly labeled "Sister Ray" before Scarlet names it.
Just before Cloud jumps into the train he is surrounded by Shinra soldiers. However, in the FMV where he jumps, there is no trace of those soldiers anywhere near him.
At one point when Jenova speaks to Cloud (with white text on a black background), the word 'because' is incorrect. The text in the game is: "Beacause, you are.....a puppet."
In the Wonder Square at Gold Saucer, there's Mini Game called "Mog House". A Moogle named Mog has tiny bat wings much smaller than his body size. The player must feed him the right amount of Kupo nuts for him to fly. Flying in the air for Mog would actually be practically impossible for him to perform for a number of reasons. Since his wings don't flap very fast, he wouldn't get enough momentum to hover. Also since his body weighs more than his tiny wings, he would end up falling on the ground anyways since gravity pulls heavy objects down, even with the right amount of Kupo nuts. In order for Mog to be able to fly and overcome gravity, his wing span would have to be larger and twice the size than his body like bats have, then it would actually allow him to fly at will and overcome gravity. Even then he wouldn't even need Kupo nuts to fly, unless he's hungry or craves them.
When the final boss Safer Sephiroth casts the spell, Super Nova, the animation shows the Super nova destroying the planets within the solar system, but when it comes down to earth, Cloud and the 2 party members is somehow able to survive the intense heat. This would actually instantly kill Cloud and his 2 party members, destroy Earth and all the inhabitants living on it and would actually result in a game over. Also the giant meteor that threatens to crash on Earth in disc 2, and 3 would be destroyed or made obsolete by the Super Nova which is more powerful than the Giant Meteor. It's unknown why Sephiroth summoned a giant meteor to crash on Earth when he gains the summon Super Nova that can just as easily destroy countless planets.
When Cid aborted the Rocket Launch mission, the rocket leaned over on one side and it would've fallen over. Also why did Palmer and Rufus launch the rocket at a leaned angle instead getting the rocket to stand up straight. The gravity would've pulled the rocket and it would not been able to overcome gravity as well and would've risked crashing into the ground instead up being launched successfully up into space.
When Cloud and his party members travel in the Icicle Area they are not dressed up for winter and Cloud wears a sleeveless shirt, even when they pass by Icicle Inn village and when Cloud Snowboards down the hill, also when they travel in Great Glacier and climb the Gaea's Cliff they still are not dressed up for winter. Also Cloud would pass out much sooner than later on. It's unknown why they didn't buy warm winter clothes which would've prevented Cloud from passing out.
If the party encounters the super boss Emerald Weapon while in a submarine, they will get out of the submarine and fight it on foot underwater. It wouldn't be possible to fight underwater, not without diving suits with oxygen tank anyway, also they wouldn't be able quickly attack with weapons as the water would slow down their movements making attacking useless. Also they would drown after a few minutes instead of 20 minutes. Even with diving suits they would be more vulnerable to Emerald Weapon attacking and damaging their diving suits.
Many of the bulky gigantic swords that Cloud Strife uses including the Buster Sword would be impossible and impractical to wield in real life as he wouldn't be able to lift it, let alone run over to an enemy, even if he swung it down on an enemy, he wouldn't be able to jump back with the sword, it would likely cause back injury. Cloud would've been better off with a lighter sword like a long sword, rapier or katana as they are easy to wield and swing around and would kill monsters than the gigantic sword used in the game.
When Sephiroth joins Cloud in the flashback sequence, he is seen fighting with a sword called Masamune which is longer than his height. It would be hard to wield and swing or stab, due to it being extra long, also it would wobble a lot which may make it harder to land blows on an enemy. If his sword was shorted down less than his height, then his sword would be much more practical to use, even in real life.
In the motorcycle chase scene, Cloud Strife gets on a motorcycle and escapes Shinra Headquarters. In the mini game including the arcade game G-bike, Cloud is seen swinging his huge buster sword left and right while riding his motorcycle on the freeway. This would not work as the huge buster sword he swings would actually pull Cloud on the side and cause him to crash. It would've been better if he used a much lighter thinner sword to knock the red and yellow Shinra soldiers down and it wouldn't pull Cloud down like his heavy oversized buster sword would.
How is it possible for Cloud and his party to fly all over the world and not get shot down. Especially if they fly over big cities like Midgar or Junon which the Shinra Soldiers would shoot the airship down with missiles, it's unknown why the Shinra soldiers don't shoot the airship down since it was stolen from the Junon airport by Cid and the pilot workers and Shinra would've hunted them down for the airship.
When the sneak attack materia is used with Barret, the line in the text box on the top of the screen reads: "Barret was cought by surprise!" the correct spelling is CAUGHT.
When Cloud and his 2 party members Tifa and Aeris arrive in the village of Gongaga in Disc 1, they meet Zack's mother and father who say he hasn't contacted them over 10 years. Aeris and Tifa run out of the house upset and Cloud talks to them. Later on if Cloud goes in the basement of Nibelheim mansion they are introduced to a flashback of how Zack got killed outside of Midgar being shot to death. But when Cloud goes back to Zack's parents they still have no idea that he was murdered by Shinra Soldiers and Cloud never tells them the news, neither does the Shinra Soldiers or the messengers from Midgar. It's unknown if Zack's mother and father ever got the news of their sons death at Midgar as the News reporters would've reported the news of Zack's death on TV and they would've got the newspaper article or a letter on Zacks death.
When the party obtains 2 vehicles, one of the all terrain cars is called Buggy while the shot down airplane Tiny Bronco is used as a boat during Disc 1 and the beginning of Disc 2. If the party gets the Airship called Highwind. Their Buggy and Tiny Bronco disappears from the game. It's unknown if the Shinra company stolen the 2 vehicles and confiscated it as the game doesn't explain for the disappearance but they're obsolete anyways as the Highwind can fly anywhere in the game.
When Rufus visits Rocket Town to meet with Cid, why did he need to use the Tiny Bronco when he can already ride in a helicopter or in the Highwind Airship.
In the Sector Five slums, Cloud will stop outside the pipe containing the sick man, and Aeris will say, "This guy are sick."
In the Gold Saucer Battle Arena, during the speech involving Cloud, one of the characters incorrectly says "Off-course!" instead of "Of-course!".
One of the accessories called Tough Ring is misspelled as Touph Ring, which was fixed in later PC versions.
During the Temple of the Ancients quest. A misspelling appears in the game script when Cait Sith says to the party "I'm so exited." instead of "I'm so Excited."