A guy who can appear to be anything, and he chooses this?
The manipulative master of special effects
is capable of constructing any illusion and staging any scene that serves his diabolical plans.
Mysterio has to have the dumbest motivation of any Spider-villain (other than Venom): he was the best effects man in Hollywood, but decided to fight Spider-Man because he felt that he wasn't receiving enough fame for his work. You know, because hyper-talented special effects artists never become independently famous. Rick Baker, Stan Winston, Ray Harryhausen, Greg Nicotero, Tom Savini... you only think you've heard of those guys, you really haven't.
There hasn't really been a Mysterio figure since ToyBiz made one, and while the body on that figure was great, the design of the head was a mess. The character's defining characteristic is his fishbowl helmet, and they managed to get the shape of it wrong. You'll be happy to know that this one does things just right. The dome is just that: a spherical dome, not some straight-sided thing. And it's pearly white instead of smoky grey! Much better.
The body below said dome, however, is not as impressive an accomplishment: it's the same mold used for Daredevil and Bullseye, which means that while it's nicely sculpted and
has plenty of articulation, it's lacking the "quilted" pattern his costume has always tended to have. He does have the advantage of new gloves slipped over his forearms (with the intricate, swirling pattern sculpted on all four sides), and his cape has an all-over texture that makes it look heavier than the average superhuman shawl. Is he wearing velvet? It fades from a rich purple near the collar to minorly translucent near the lower edge - perhaps to suggest he's standing in fog or something?
The cape and fishbowl are both separate pieces, but there are tabs on the cape that fit into notches on the helmet, to help keep it in its proper place. If you remove it, though, there's a surprise waiting beneath! Hasbro gave the figure a real head, and rather than just reusing a Silver Surfer head or something, it's a new sculpt - of a new character!
Judging by the nigh-skeletal nose and the seam that runs all the way down the center of his head, this head belongs to the Chameleon! Yes, it's molded in dark green, rather than white, but the design is unmistakable. There's never been a 4" Chameleon, so it's not like this was something that was just sitting around - was Hasbro planning to make a Chameleon and it got scrapped? Or was this just an Easter egg they made specifically for this figure, figuring that it was a good way to get another Spidey villain - one who may not be toyetic enough for a real release - into the hands of fans, even if only as custom fodder?
If that was the plan, though, good luck; Mysterio was released at the end of the Marvel Universe line, and so never reached stores in numbers large enough for most people to even see one, let alone find a second to pop the head off of. If you can find Mysterio, though, you'll be one step closer to completing your 4" scale Sinister Six - even without his quilty body, this is a nice representation.