There is an unused female version of somebody humming the Hymm of the Fayth, as hummed by Tidus during the game, on the game's disc. It is unknown who the voice could be.

Tidus is never actually directly referred to by his name in audible dialogue. People will refer to him with impersonal pronouns. This is due to the player being able to name Tidus at the start of the game, and this being Square Enix's first voiced Final Fantasy game, they weren't sure how to handle a variable name. Tidus' name pronunciation has been debated, but was confirmed to be pronounced "Tee-Dus" by James Arnold Taylor, the voice actor for Tidus.

At the end of the game Yuna will proclaim to Tidus that she loves him. However in the Japanese version Yuna will simply thank him. This change was to make up for cultural differences.

Final Fantasy X was the first core Final Fantasy title that wasn't entirely composed by Nobuo Uematsu. The score was also created by Masashi Hamauzu and Junya Nakano.

Lulu's starting weapon, a Moogle Doll, is the only appearance of a Moogle in the game, a massive difference from all previous titles in the series. Her other weapons are references to previous characters in the series, including her final weapon of the Onion Knights from Final Fantasy III.

Character designer Tetsuya Nomura has said that the South Pacific, Thailand and Japan are major influences on the culture and geographical design of Spira, particularly in the case of the southern islands of Besaid and Kilika.

In Tidus's early development, he originally had darker colored hair. It was changed, most likely because his name means "Sun" in Okinawan, and the developers wanted the color of his hair to reflect that.

Lulu's dress in Final Fantasy X was designed by Tetsuya Nomura specifically to see if the graphic designers could keep the exact number of belts in the right places every time. This is why many cutscenes with her show Lulu from the waist up or from behind.

Cloud's Buster Sword was originally intended for use by Tidus but was removed before the game was released. It is still in the game's code, though, and using hacking tools, it can be obtained and used in the final version.

When you talk to the woman taking care of the Chocobos at the bottom of the ship during the sea voyage to Kilika, she will sing a part of the Chocobo Theme.

During the fight with Spoiler:Seymour Omnis inside of Sin, summoning Anima will provoke a response from Seymour, "You would oppose me as well? So be it." He says this because Anima was formerly his final aeon, as well as his mother.

Final Fantasy X, like other games in the series, features many references to real world religions and their history. This game in particular alludes to the conflicts between Christianity and Gnosticism; it also depicts the corruption possible within organized religion, and how it can lead to an inversion of its own doctrine.

Auron's voice actor, Matt McKenzie, is also the voice of Major Elliot from Final Fantasy: The Spirits Within.

In a 2001 V-Jump magazine interview with the game's character designer Tetsuya Nomura, he said that when designing Tidus' emblem, he thought of various things related to the ocean, like fishing hooks, fishbones, whale fins, and based his designs about them. He mentioned that Tidus' necklace is the emblem for his blitzball team, the Zanarkand Abes. And also stated that he came up with the idea before the Al Bhed language was written, but the shape design of the necklace is actually the combined letters of "T" + "J" from the start of Tidus & Jecht's names.

In a 2001 V-Jump magazine interview with the game's art director Yusuke Naora, he was asked where the idea for an "asian" themed world came from? He responded:

According to a 2001 V-Jump magazine interview with the game's designer Fumi Nakashima, she stated that her inspiration for the Al Bhed’s clothing came from bondage fashion. She recalled having various bondage books and magazines on her desks at work and her co-workers giving her "weird looks" in response to seeing them.

According to a 2001 developer interview published in V-Jump magazine, the game's composer Nobuo Uematsu stated his team started including theme songs in the Final Fantasy games since Final Fantasy VIII, and that each time, Uematsu & Yoshinori Kitase would hold a meeting to decide who would sing the theme song. The developers brought in various music CDs of singers they liked to listen to and would share their opinions. At some point during the meeting for Final Fantasy X's theme song, they could not decide on who to pick. Around the same time, a member from their staff happened to buy one of Rikki’s independent releases at a CD shop, and showed it to Uematsu. He loved it after listening to it, and said in a excited mood "This is great!", leading the team to contact Rikki right away to perform the song, called "Suteki Da Ne", for the game. Uematsu considered it a memorable song for FFX, and that from the beginning the music would be a central part of the soundtrack.

At the 2017 Emerald City Comic Con during a panel with American voice actor John DiMaggio, he explained that he was told to make Wakka's voice sound like an islander, with an island accent. At the time, he broke up with his girlfriend from Hawaii, so he came up with some Hawaiian impersonations which landed him the role of Wakka.

According to a 2001 developer interview published in V-Jump magazine, the game's character designer Tetsuya Nomura stated the main character's name, Tiida (Tidus in the international release), was the Okinawan word for "sun". After Final Fantasy VIII, the team wanted to give their next main character a brighter and more cheerful personality. Kazushige Nojima gave Tiida his name, and Nomura thought he had a "bright" motif for the character in mind considering his name's meaning.

In a 2001 interview with the game's character designer Tetsuya Nomura published in the V-Jump magazine, he stated that he used the same approach to making character designs from Final Fantasy VIII for this game. The first thing he did was draw just the character's face, and then he discusses with the team on how "realistic" the design should be. After that he'd asked about the backstories for each character and use that to figure out the details of their designs; for example asking if they were an athletic, sportsy type, or are they are a summoner type of character. Nomura also stated that a big consideration for the game was that the world has an "Asian" vibe to it, so he tried to be conscious of that style while at the same time making sure the main characters didn't look too familiar between each other. The team asked Nomura that he only made the main protagonist Tidus stand apart somewhat from the overall world, so Tidus' design is very distinct from the Asian aesthetic.