Angst? What Angst?: When the twins' missing memories returned to them, they do suffer from My God, What Have I Done? for a brief bit, but in random battle's they're still joking and bantering with no sign that this is just an act they uphold for each others' sake and then the Reset Button is mashed with great haste with zero permanent effect on gameplay.
Big-Lipped Alligator Moment: In a dialogue exchange in Nine Woods Hills, after Tama explains about Mirage Mastery, the characters- one-by-one- break down laughing over the idea of "Master" Lann. It gets so contagious that Enna Kros randomly pops in and asks if she really chose the right people to save Grymiore before joining in the laughing too. It is, of course, never brought up again.
Fridge Brilliance: Eiko showed up at Cornelia during one of the intervene quests when the Cogna arrived. For those who don't look into secrets in Final Fantasy games, it won't make sense why Eiko is seen with Princess Sarah. But if they do, they will know the Easter Egg. What is Princess Garnet's a.k.a. Dagger's real name?
Hilarious in Hindsight: Pokémon Rusty already used the whole 'have-your-mons-stack-together-to-fight-others' concept back in 2014 (in the Battlehaus episode, where Rusty was being taught the battle styles the facility uses). Square Enix just took the concept and based a whole game around it.
Moe: The artstyle is this, with all the chibi-fied characters and even traditional Final Fantasy summons and monster looking ridiculously cute.
Narm: Whenever Lann and Reynn are in their chibi forms or there are other chibi characters in them scenes can be really hard to take seriously, even when there's some dire threat or disaster or whatever looming.
This game marks one of the first mainstream appearances of a female Ifrit, but the concept has been around for a while. An "Ifreeta" card shows up in Mobius Final Fantasy, a game released earlier in 2016 in the US,note Though she's much more humanoid there. and certain incarnations of Ifrit have been depicted as female in certain spin-offs and crossover games, such as Million Arthur, which had a card named Heatra, who was basically a gender-bended, less animalistic version of Final Fantasy X's Ifrit.
Periphery Demographic: The creators have stated that this game was made to try to appeal to the younger crowd, as the franchise wasn't exactly very popular with them. In spite of this, the game caught the eye of veteran Final Fantasy fans for using the classic battle system, which many have been clamoring for the series to use again after the shift to a more action-oriented fighting style.
Polished Port: The Maxima port for the Switch is a portable version of the console releases, but with added content (which can be bought as DLC for other versions, but still). The Sora DLC isn't on the Switch version, though.
The Scrappy: There are fans who find Tama to be extremely the-annoying, partly due to her the-Verbal Tic.
Surprise Creepy: This image that's shown at the end of the bad ending before the player is kicked back to a silent title screen.
The intervention quest "The Five Cogna Lords: Figaro" requires you to play basically Battleship on a 5x5 board. You don't need to beat it to continue the story, but to get the Maduin Memento you have to beat it in 20 turns or less, without losing a single unit (your enemy's turns are included in that number, but since you can only win on your turn, you've effectively only got 10 turns). You and your enemy both have three units, with 1, 2 and 3 hp each, meaning you can only spare missing four times, as you need the other six to actually take down all their hp. It's so infamous that the notes on the Maxima expansion specifically state they made this mini-game easier.
The Four Stars Intervention: Sunken Temple's Secret Quest about Shantotto and Cenchos plays like this if you try to game the system. Shantotto is meant to be a Hopeless Boss Fight, but is technically defeatable and has scripted drops. She does, however, have three times as much HP as XG, and defeating her means you go into the consequent battle with Cenchos at the HP and AP levels