Cid, a recurring character in the series who is usually a mechanic with some relation to airships, first appeared in Final Fantasy II and did not appear in the first Final Fantasy game. For the Final Fantasy I & II: Dawn of Souls re-release however, the original game's plot was retroactively changed to make "Cid of the Lufaine" the ancient creator of the airship that the protagonists used.

The Final Fantasy series' title was long rumored to stem from the idea that it would've been Square and series creator Hironobu Sakaguchi's final game if it didn't perform well. According to these claims, Square was in dire financial straits in 1987, with Sakaguchi planning to quit the gaming industry and return to university studies. These claims appeared to be further corroborated when series composer Nobuo Uematsu affirmed them in a 2009 interview with Wired, claiming that Square's financial position was the main inspiration for the Final Fantasy name.

However, Sakaguchi debunked the rumors in a 2015 keynote address. In reality, Square always intended to give the first game in the series a name whose initials were "FF," as the Japanese pronunciation, エフ・エフ ("efu efu"), was considered pleasing to the ears. The developers' initial pick was Fighting Fantasy; however, it turned out that this name was already taken by a tabletop RPG series. Consequently, the title was changed to Final Fantasy. According to Sakaguchi, while Square indeed had their "backs to the wall" during development, "anything that started with an F would have been fine for the title."

Pressing A and B 55 times while on the ship will unlock a hidden sliding puzzle game.

The miniboss Eye or Evil Eye resembles the monster Beholder from "Dungeons and Dragons" and was named Beholder in the original Japanese version of the game. Due to copyright concerns, it was renamed and redesigned for all other versions.

The spell Saber (SABR in the NES version) does nothing in the NES version. In later releases, it increases the caster's attack by 16 and the caster's accuracy by 10.

The spell Temper (TMPR) was bugged in the original NES version. In later releases, it raises the attack of an ally by 14.

In the NES and PS releases of the game, Intelligence had no effect on a spell's strength. A Red Mage can do as much damage with a fire spell as a Black Mage, and can use a cure spell as well as a White Mage, even though a White Mage should be better at it.

In the NES release of Final Fantasy, there is a glitch in Cornelia Castle where the player can trigger a text dialogue without there being a sprite to talk to.

In the English version of the game, just outside the city of Elfheim/Elfland are three tombstones, one which reads:
"Here lies Erdrick
837-866
R.I.P."
Erdrick is referenced a lot during the game Dragon Quest, and is also the hero in Dragon Quest 3.

In the original Japanese version of the game, the tombstone is actually a reference to Link from the Legend of Zelda series. In later remakes of the game, the reference has been changed back to Link.