Ready for a three-story outdoor theater in Union Square? Well, the former Virgin megastore is transforming itself into just that on October 28th, when Marvel Comics takes over the outdoor wall to premiere its "Astonishing X-Men" motion comic on the building.

The off-the-wall screening is all part of the company's first Marvelfest, taking place in Union Square Park. "The event will feature several high-profile Marvel Comics creators, including X-Men artist Neal Adams and Spider-Man writer Dan Slott, a costume contest and various giveaways," according to the Post. Marvel VP Mike Pasciullo says, “MarvelFest NYC 2009 is a once-in-a-lifetime experience for anyone who loves Marvel’s great characters. This is something that’s never been done in the comic industry and we can’t wait to see how New York turns out to celebrate."

Get more details on the event here, and if you decide to geek out that weekend, please send us your photos of that costume contest!