Development Gag: An obscure one for Edward's English name — it was borrowed from the name given to Richard (incidentally a Highwind) in the NES prototype of Final Fantasy II.
Doing It for the Art: The original plan when making the English port of the DS version was just to text dump the game's GBA script. Translator Tom Slattery, however, was a fan of the original SNES version of the game, and offered to single-handedly re-translate the entire script from Japanese to give it more flair and be more faithful to the original Japanese story. His hard work is noticeable.
Fan Nickname: The game is occasionally called Die Hard among speedrunners, due to the 64 stairway trick mentioned in the main article.
No Export for You: For some strange reason, the Steam version isn't available in Asia. Thankfully, the other versions of the game (iOS, Android and DS) are.
As with the other Final Fantasy titles, the original Super Nintendo version skipped over Europe, and Europe only got to play the game when it was ported to the PlayStation.
It was rumored that in the original (i.e. Japanese) version of the game, it was possible for Cecil to de-petrify Palom and Porom himself, by following some convoluted method which, depending to who you heard it from, may involve the very real Developer's RoomEaster Egg. You can't. It doesn't help that the game teases you by giving you an option to choose an item to use on them if you interact with their petrified form; no matter what you use, nothing will happen. (This is a holdover from the Japanese version, where you still couldn't actually accomplish anything but where there was at least a special message if you tried to use a Golden Needle to help them in an acknowledgement of the usual headscratcher of using curative items to reverse a Plotline Death. Since the Golden Needle was Dummied Out in the American/Easytype release, even that bare message is unavailable.)
Managing to obtain Dark Matter before using the Crystal on the Final Boss (or during any phase in the iOS version) does not blunt the power of Zeromus's Big Bang, contrary to popular belief. Using the item has no effect, but the rumor persists regardless, even on This Very Wiki. In a likely nod, Dark Matter does serve a purpose in the 3D remakes: if the player has the item in their inventory during New Game+, landing the Lunar Whale on the surface of the Red Moon and using the item when prompted leads to an encounter with one of the game's superbosses, the Proto-Babil.
Supposedly, the SNES version had roughly 25% of the intended script. The remakes (especially the DS in 2008) went on to expand the script (which, it turns out, is largely to the benefit of fleshing out Golbez, which is why he serves as the remake's logo). This isn't near the remaining 75% that was apparently abandoned, however.
There's also the unreleased Family Computer version of the game (allegedly an entirely different game, with this Super Famicom concept initially "Final Fantasy V"), which, despite original projections, was actually 80% complete before it had to be shelved. From the sound of things, certain ideas were reused for the released Final Fantasy IV and Final Fantasy V, but Hironobu Sakaguchi still regretted that he had to let it go.
Disney originally commissioned a comic series based off of Final Fantasy IV back in 1991 which never materialized. This became Hilarious in Hindsight over a decade later with the advent of Kingdom Hearts.