Elon Musk has often been compared to Tony Stark. The billionaire entrepreneur is the brains behind SpaceX's reusable rockets, Tesla's electric cars, and the solar power provider SolarCity. But last night when comedian Stephen Colbert pressed Musk to decide whether he's a superhero or a supervillain, Musk was evasive.

Today in "Robert Downey Jr. saves the world," the Hollywood superstar presented an Iron Man-style bionic arm to a young disabled boy named Alex.