Generator Rex

[Dragon FangX]

Not sure where Generator Rex fits into. It has transformation in that the main character, Rex, can create machines from his body that have multiple uses, you have many people who turn into giant monsters, though usually you only see the after math as Rex, able to cure them, reverts them to normal, and you have a hot goth chick who's mouth turns into a giant leech mouth...

... So yeah, treat Rex as you may. I think its a promising show to keep an eye out on for transformations.