There’s a lot of supposition in this story, but it looks like a LEGO presentation at the London Toy Fair has spilled the beans on an as-yet-unannounced villain for this summer’s Iron Man 3. The website Brick Fanatic described one of the Lego Iron Man 3 kits on display as containing:
Tony Stark, Iron Man mk42, Pepper Potts, Mandarin and a pale green bad guy we were not allowed to know the name of.
Bleeding Cool speculates that the character in question may be Radioactive Man, the Marvel character, not the one from The Simpsons. Xueqi Wang was once rumored to be playing Chen Lu (Radioactive Man’s alter-ego) in the film, but was later listed as ‘Dr. Wu;’ though that could easily be a simple name change, or out-right misdirection.