Posha is the only playable character with two different sets of battle sprites. One for when her hair is long, and the other for when it's short.
The only playable character you never use in Toxa's Quest is Troy. He does appear several times in the story, but you never actually use him in battle. Lacryma and Bachstail are both used once in the Mystic Forest battle. Kun is used in the Arena Battle and the River Battle right after that. Rimzan is used in the Kainas Marketplace Battle. Ele is used for the first few battles of the game. And, of course, Toxa, Alana, Duran, Misty, and Posha are the main characters for almost all of the battles until Karis replaces Duran near the end.
The only playable character you never use in battle in Lacryma's quest is, ironically, Toxa.
Cross has a facial expression that makes him look nearly identical to Alex in the beginning of "A Clockwork Orange".
Blooper: Posha appears with short hair in a between-chapter story segment before she actually cuts it. (This is when the game shows a full-body still of the character while text is displayed to the left.)
Blooper: Duran says he's glad they got Misty back in a between-chapter (full-body still) story segment before the battle where they actually rescue her.
Kartia was called "Rebus" in Japan. It was made by R&D1 and published by Atlus in both Japan as "Rebus" and America as "Kartia". However, the game was publised in Europe by Konami with the title "The Legend of Kartia".
Kartia's package art gives it the subtitle "The Word of Fate", however this subtitle never appears anywhere in the game. Toxa's Quest is subtitled "The Record of Fake" (possible spelling error?) and Lacryma's Quest is subtitled "The Record of Fate".
Kartia's music was done by two different composers - one for the battle music and one for the story music. (However, I'm suspicious that the battle theme composer may have also done at least some of the story themes, as I can hear two distinctly different styles of music used. Some sound closer to the same style of the battle themes than the others.)
Due to a glitch or a mistake in the game's programming, it would seem impossible to get the Fynus phantom to use in battle, although a screenshot on the back of the game's packaging shows your characters using Fynus phantoms in a battle.