his character works well, especially compared to alot of the other characters (who are fairly one-dimensional)
Chrono likes to beat things up with his sword/holy magic of doom, ends up picking a fight with lavos, getting disintegrated, comming back, and whuppin ass. fairly boring
Marle grows up a bit but its a typical "my father is a douchebag" attitude to "my father is sort of a douchebag but he's also not a dumbass"
Lucca has the bit with her mom, but by and large we don't track her changes, she starts out a nerd, ends up a nerd with a bigger gun
Ayla likes to hit stuff, that dosen't change that much
Robo starts out a good robot, ends up a good robot who found out that all this time he's been disobeying his programming, and then responds with "fuck you" to mama brain.
Frog (my favorite) on the other hand starts out as a little kid who's a pacifist because even though he's damn good at it (storyline wise, gameplay i actually find him to be on the lower tier, chrono mags and robo are my smackdown party), cause he dosent wanna hurt people. then cyrus gets killed and glenn turns into frog and becomes sworn protecter/revenge knight on mags (with a bit of emo depression thrown in, but he dosen't get toooooo wangsty). eventually he learns that sometimes hitting people in the face with a nice sword is less about hurting and more about protecting and goes off to go stab cthulhu in the face with a shiney sword.
magus we first see as a generic monster/wizard thing. and we think at first he's nothing more than a really tricky halfway boss. then we find out that "oh shit, he's not lavos's creator after all, he was summoning him for some purpose or another" (we don't find out immediately that he wants to summon lavos to dark matter the shit out of him). then we meet him again (although we don't know it) both as kid janus and as the prophet. we find out kid janus is huuuuuuuuuuuuugely dependant on his sister, even if he is sort of a douche. then WHAM! the ocean palace goes to shit, lavos royally fucks up everyone's day, and then we find out that magus and janus are the same person, and that magus had his goals aligned with the party's all along (and to think, if they had just talked they could have saved alot of lightning bolts to the face on both ends).
now that's a bit of a character arc
plus it don't hurt that he's got the coolest spells in the game