In the world of ruin, in Narshe, it is possible to get the Ragnarok Esper, and have a one-of-a-kind sword made out of it. Later on in the game, it is possible to steal the same sword from an enemy.
In the Cult Tower, you can faintly see through the windows out to the background, even though you should be seeing the inside of the wall.
After Terra escapes in in the backdoor of Arvis house she runs in the mines of Narshe, but when the Narshe guards surrounds her and she falls down in the doorsteps of the Moogles room. It's unknown how the Narshe guards coming from the west side of the Narshe Mines got into the secret entrance passage that Locke knew about. Also the guards would've headed straight down into the room Terra fell while Locke came to the rescue without fighting the guards.
In Thamasa at night when Relm gets trapped in the Burning Home. Strago, Locke and Terra goes inside the house. But there's no time limit or the party slowly losing HPs to the inferno heat around. Yet later on in the World of Ruins the crumbling house in Tzen has a time limit.
How is it that Sabin's path is longer than Locke's Path and Terra Path but he's somehow able to meet up with Locke's group and Terra's group at the same time, which probably kept them waiting in Narshe for a long while.
The evasion stat is useless. All evasion is calculated with the MBLOCK stat instead. This also makes the beads relic worthless. This error exists on the SNES and PSX incarnations, although there are ROM patches for the SNES version to fix this.
After Banon, Arvis arrived in the burning capital of Vector. They are not seen again after Kefka attacks the Espers in Thamasa and the floating continent raises up and during the end of the world sequence and in the World of Ruins. It's unknown what became the fate of Banon and Arvis if they were killed or if they survived and if they did, they have gone missing and they aren't seen in the ending of Final Fantasy VI.