VIDEO : Chris Evans, Chris Hemsworth Discover Which Avengers: Age of Ultron Star Has Bigger Biceps T

It takes quite a muscular man to make Chris Evans and Chris Hemsworth jealous?an Iron Man, actually.
Yes, let's give credit where credit is due: A photo of Robert Downey Jr.'s arm gave his Avengers: Age of Ultron co-stars some serious bicep envy!It all came about innocently enough when MTV News' Josh Horowitz invited the superhero gang to play a guessing game to see how well they know their biceps. It was Downey's bulging bicep, though, that had his fellow beefcakes in disbelief!??