Mark Ruffalo as Newspaper Editor: The Kid's All Right

Actor acts as worthy guest-editor-in-chief of New York's Metro for Earth Day

Mark Ruffalo — the Oscar-nominated actor who was cast to play the "Incredible Hulk" in the upcoming "Avengers" flick — took on slightly different "green" role than he's used to this week: editor of New York's Metro newspaper.

Ruffalo acted as guest editor for the free daily's April 22 "Earth Day" issue. And unlike some other celebrity editors-for-a-day (I'm looking at you, Bono) Ruffalo played the role well, sitting in on the daily newsroom meeting, marking up the "Earth Day" copy (which the paper ran alongside each story) and penning a column on the dangers of "fracking," — the "hydraulic fracturing" or drilling for natural gas underneath the water supply, something that's become a huge issue in upstate New York, where Ruffalo and his family live.

"I had never thought of myself as much of an environmentalist, and I didn't imagine myself as any kind of journalist," Ruffalo wrote in his editor's note, "unless perhaps I played one in a movie."

But as anyone who follows Ruffalo on Twitter (@Mruff221) already knows, the "Kids Are All Right" star is passionate about environmental issues — particularly this one. He recently launched a website, WaterDefense.org, to draw attention to the issue.

"[Fracking] is extremely risky," he wrote. "Across the country it has led to water contamination so severe that people can literally light their water on fire."

Ruffalo added: "It's just crazy to me that our society would allow clean water to be destroyed."

It wasn't all serious editorial with Ruffalo at the helm. He contributed an online-only post — "Mark Ruffalo Porn Titles, By Mark Ruffalo" — that disclosed some alternative NSFW titles for his movies (obvious-but-effective example: "In the Butt").

Not surprisingly, he managed to score a separate write-up in the "Earth Day" issue for "Sympathy for Delicious," Ruffalo's upcoming directorial debut — which he also stars in.

"After I was done, I was like, 'I'm not acting anymore. All I'm going to do now is direct.'"