Robert Downey Jr. plays the super hero Iron Man on film, but to 7-year-old Alex he's a real hero. In this video, Robert Downey Jr. delivers a real, 3D-printed bionic arm to Alex, who was born with a deficient right arm. Alex's new bionic arm lets him be just like his hero, Iron Man. He can grip with new fingers and an opposable thumb. His new arm even has a light built into the palm so he can blast away bad guys just like in the movies.