Green Lantern, Nathan Fillion

He's enjoying mainstream success as the star of ABC's Castle, but Nathan Fillion is still a fanboy favorite — and a fanboy himself. So the Firefly and Dr. Horrible alum totally geeked out when he was offered the voice role of DC Comics superhero Green Lantern in the DVD movie Green Lantern: Emerald Knights, due June 7 from Warner Bros. Animation. Emerald Knights is a series of vignettes about the Green Lantern Corps, an intergalactic police force. Fillion plays Hal Jordan, the Green Lantern of Earth's space sector, who mentors Arisia, a new recruit played by Mad Men's Elisabeth Moss. "I was always reading the comic books, I was always a spectator," Fillion says. "Now I feel like I own a little piece of Green Lantern."

And he's getting to share it with an old friend, Ryan Reynolds, who is starring in the Green Lantern feature film, which opens 10 days after the DVD comes out. Both actors got their big breaks together on the ABC sitcom Two Guys and a Girl. "He's a great guy, a gem, deserves all the success that he's getting," says Fillion, "so it's neat to have a little piece and share it with someone you know.

The voice cast for Green Lantern: Emerald Knights also includes Jason Isaacs (Lucius Malfoy from the Harry Potter movies), Kelly Hu (Hawaii Five-0, The Vampire Diaries), actor/spoken-word artist Henry Rollins and ex-wrestler "Rowdy" Roddy Piper.

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