I was made aware of a really interesting glitch in Tales of Symphonia, which is most likely due to an oversight by the programmers. It's nothing gamebreaking, it's just really funny, that's all. Since spoilers are involved, I'm going to hide the whole thing behind a jump, despite this being a 2003 game. Am I not just the nicest guy ever?
In the Temple of Darkness, there's this hole that leads to the altar where you can change the Sorcerer's Ring's function. When you enter that hole, the character with the highest affection score appears and tells Lloyd to be careful and whatnot. Well, if you choose to talk with Kratos in Flanoir, you end up killing Zelos not long after. But guess what? If Zelos is the character with the highest affection score and you return to the Temple of Darkness (which you have to do for the Abyssion sidequest, no less), if you try going into that hole, Zelos will appear, even though he's dead. Well done, Namco, well done. I imagine the glitch has actually been executed by only a handful of people, because of how hard it is to have Zelos like you the most (usually if you're shooting for Zelos as soulmate, Raine will be the one with the highest affection), and the fact that you just don't need to go through that hole while going for Abyssion, but it's there.
Related quirk: if Kratos is in your party and you go through that hole, he will stay in your party, even though Lloyd should be alone. This is because the game was programmed to remove Colette, Genis, Raine, Sheena, Presea, Zelos and Regal individually, but NOT Kratos, since he's not in the party during the mandatory visit to the temple. Oops. Extra points if Kratos is your highest affection character, because Lloyd will tell him to stay there, but he won't.
As an added bonus, there are ways to alter each character's affection even after the Great Seed Dungeon... including Zelos, regardless of whether he's dead or alive. So yeah, Zelos is still judging you even in the afterlife. Of course it only makes a difference in New Game +, since the fortune teller in Triet won't tell you anything about Zelos if you kill him off, and affection is only really important up until the Flanoir scene anyway.