Beloved actor Nathan Fillion climbs aboard the Percy Jackson film series in Sea of Monsters, and director Thor Freudenthal says working with the star was a treat.

Like many, Freudenthal was a big fan of Fillion’s body of work – most notably Firefly and Dr. Horrible’s Sing-Along Blog.

“I was a huge fan of Nathan Fillion, and now that I’ve worked with him I’m an even bigger fan of Nathan Fillion,” Freudenthal told us. “I watched an old episode of Firefly after I watched all of Dr. Horrible’s Sing-Along Blog in one sitting and his work is just amazing.”

The director said that Fillion, who plays Hermes, brought a lot of what fans already love about the actor to Sea of Monsters. “He’s got razor sharp comedic timing. He does a lot of his own tweaking of dialogue and writing. Literally you can tell him ‘Okay you have to cross from here to there, but we don’t have enough words to fill that.’ So he’s like, ‘Okay I’ve got something’ and then it’s the funniest line in the scene.”

Sea of Monsters wanted to balance action with light-heartedness, and Fillion was the ideal person for the latter. “I think he fit the tone very much of the whole movie. He doesn’t take himself too seriously, but also this character of Hermes has deep regrets when it comes to his son Luke who is clearly the bad seed. Hermes would rather forget about the wrong choices he made with that kid. But it sort of weighs him down.”

Fillion has one moment that fans of Firefly will particularly love: Hermes makes a direct reference to his beloved science fiction show. After we noticed it during our screening, we asked Freudenthal how that line came to be.

“I worked with a great writer on this film, and I told him that we would cast Nathan. And he instantly went back to the computer and revised lines. He actually wrote a very direct Firefly reference into it that had Hermes say, ‘Hey, the best show ever is Firefly.’ And that really takes you out of the movie. So while it was a great sort of general direction to go in, Nathan came up with ‘Greatest television show ever so of course, canceled.'”

Percy Jackson: Sea of Monsters enters theaters Wednesday, August 7.

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