Just something that made me wonder:

In the Comic, people from the Chrono Trigger Universe have to do an oral incantation. So, how does Crono do it?

Well, Lucca seems to be able to understand what Chrono means when he says "..."; maybe he's speaking null, or something.

If you notice, only Magus seems to be moving his mouth when he casts spells, though. If I recall, anyway. . .

Crono has his mouth wide open when he casts luminare, maybe you're just confused.

Lucca just does a little dance to cast fire, and Marle doesn't seem to do anything at all...

You know. . . I am confused. Slightly.
Chrono yells when he casts Luminare.
Marle prays/chants when she casts Cure/Cure 2.
Lucca twirls when she casts Flare.
Glenn(Frog) croaks when he casts Giant Frog.
Robo pounds on his chest and spins around when he casts that laser attack of his.
Ayla likes to scream or otherwise make a show when she does something.
Magus chants when casting spells.