Update: It’s definitely something to do with “Uncharted.” Fillion posted another image on his Instagram Thursday, which you can see above. More details below. “Castle” and “Firefly” Actor Nathan Fillion made his geekiest fans flip Wednesday when he posted a clue on his social media hinting that he might be involved in something connected to the “Uncharted” video game franchise. And he did it again the next day, this time with an unmistakable reference to the series.