Marvel comics have a long tradition of a new person taking up the mantle of a superhero who has passed away or retired. In following with this tradition, the Marvel Cinematic Universe has introduced a new Captain America, Sam Wilson, or the superhero previously known as Falcon. Played by Anthony Mackie, the new Captain America will be an integral part of the MCU's next steps. How did Mackie go from being a supporting character to a main one? This...