Simon Stagg. he was that way in the comics and he's that way in these two episodes. he's trying to create an genetically gifted worker that can adapt itself to any conditions. he calls this creation "Metamorpho" and he's using illegal mutagens to do this.
what a tool he is!
Orb of Ra this time, but the effect is the same. Rex can now change into any element found in the human body, or any combination thereof. of course Stagg tricks him into fighting the JLA so we can see the extent of his powers.
this is an OK episode. it suffers from being surrounded by two great story arcs. in almost any other series it would have been one of the better episode. I miss Element Girl though.