TV Brooklyn Nine-Nine: Nathan Fillion to play actor playing detective The 'Castle' vet will guest in an upcoming episode of the Fox cop comedy By Dan Snierson Dan Snierson Dan Snierson is a former senior writer at Entertainment Weekly. He left EW in 2023. EW's editorial guidelines Published on February 7, 2017 12:39PM EST Photo: Frazer Harrison/Getty Images; JORDIN ALTHAUS/FOX Brooklyn Nine-Nine is putting Nathan Fillion on the beat. Or he’s putting himself on it. The man who previously played a mystery novelist-turned-crime solver on Castle will now assume the role of an actor who thinks he’s got the skills to be a detective simply because he played one on TV, EW has learned exclusively. In a Grinder-like plot line, Fillion will pop up on the Fox cop comedy as Mark Devereaux, star of a Law & Order-y show titled Serve & Protect. When Jake (Andy Samberg) and Rosa (Stephanie Beatriz) investigate a crime that occurred on the Serve & Protect set, Mark wants to assist the detectives by drawing on his decade of experience playing a detective. You’ll even meet the executive producer of S&P, Gary Lurmax, who draws in Jake with the glitz of show business. Gary is played by another famous Hollywood face: Greg Germann, whose credits include Ally McBeal and Once Upon a Time. Firefly vet Fillion returns tomorrow night to another network comedy, Modern Family, on which he guest-stars as weatherman Rainer Shine. Fillion also appeared with Samberg in the latter’s opening bit of the 2015 Emmys. Brooklyn Nine-Nine returns for the second half of its fourth season on Apr. 11, and the episode with Fillion and Germann airs sometime this spring. The fall finale ended with a bang — a city bus knocking Gina (Chelsea Peretti). To read six reasons why she’s definitely dead —and six more why she’s actually alive — click here. Close