Swell dudes Rob and Eric are going to run a marathon, sort of. They're going to watch all eleven Marvel Studios movies --- including the upcoming Avengers: Age of Ultron --- back-to-back, and live-stream the experience, and just like the best marathon runners, they're going to raise funds for charity along the way.
Watching a lot of good movies isn't exactly hard work, of course, but that's not the point. The point is to encourage donations to Capes4Heroes, an organization that helps inspire sick kids to be brave and strong by turning them into superheroes. Rob and Eric's marathon is a way to take something that a fair number of comics fans will be doing anyway and give it positive consequences for people in need.