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. Now, 33-year-old Evans recognized his upper arm instantly. "I'd know that armpit anywhere," he explained.