Scarlett Johansson left a NYC gym yesterday with a post-workout drink. She's toning her frame in preparation to resume her role as Natasha Romanoff, the Black Widow, in the upcoming Avengers. Scarlett's costars Chris Evans, Captain America, and Chris Hemsworth, Thor, were spotted in their superhero costumes earlier this week on the Cleveland, OH, set. Scarlett wore a sensible pair of sneakers for her workout, but she's recently inspired a charitable high heel. Stuart Weitzman's "Scarlett" stiletto, from his Young Hollywood Cares Collection, was based around the actress's modern personal aesthetic.