Mark Ruffalo is best known as an indie-type actor who has appeared in romantic comedies like "13 Going on 30" and "Date Night," and most notably the critically acclaimed drama "The Kids Are All Right." So it might strike some as an odd choice for the nice guy to play mild-mannered scientist Bruce Banner, who is capable of such anger it turns him into the Incredible Hulk, an enraged green monster. But maybe that's the point. One review called Ruffalo's portrayal in "The Avengers" "a revelation, turning Banner into a wry reservoir of calm ready to become a volcano." The revelations don't stop there -- here are more surprising facts about the actor. He's an activist : He turns into a green giant in " The Avengers ." And in real life, the actor sees green -- or more likely, blue. His organization, Water Defense, works to stop natural gas drilling (fracking) and looks for cleaner alternatives. The 44-yea...