REX, Superman?
Noooooooo ..... not Superman
(wait a minute, it 'll come to me)
REX is more like a Marvel character than a DC character, he isn't simple and black & white like Superman or Batman. He isn't always successful and it certainly doesn't always turn out the way he thought it would.
He's all conflicted like Peter Parker or one of those other can't get out of his own way Marvel Superhero types.
He's a shapeshifter, that much is for sure.
Since I've known him, he's been a Savage, a Sportster, a Yammie 500 single, a BMW and a large box of parts.
He certainly can disappear and reappear ....
.... and he's like Bruce Banner, when his game is on he can be green framed and roar and kick your butt from here to the horizon ....
.... then he falters, shrinks and passes out and gets all puny again .....
.... yeah, he's sorta kinda like Dr. Bruce Banner.
And he's kinda like Merlin or a vampire, he has to go back and rest in his boxes to rejuvenate himself for the next time he has to rise and save us all again.