'Brooklyn Nine-Nine' season 4 latest news: Nathan Fillion to appear as actor playing detective

The stellar cast of "Brooklyn Nine-Nine" is about to get even bigger with "Firefly" icon Nathan Fillion signing on for a guest spot in the hit police comedy TV series.

According to Entertainment Weekly, Fillion will appear on Fox's cop comedy show as Mark Devereaux, a star of a fictional detective show "Serve & Protect," which is similar to the actual procedural drama, "Law & Order."

In an upcoming episode of "Brooklyn Nine-Nine," Jake (Andy Samberg) and Rosa (Stephanie Beatriz) will be investigating a crime that occurred on the set of "Serve & Protect." Mark, believing that he possesses the skills necessary to be an actual detective because he has been playing one on TV for a decade, volunteers himself to assist in the investigation.

Aside from Fillion, "Ally McBeal" and "Once Upon a Time" actor Greg Germann will also be appearing in the episode as the executive producer of "Serve & Protect."

Fillion's appearance in "Brooklyn Nine-Nine" is only one of several guest appearances he has recently done after the abrupt ending of his ABC TV show "Castle." He also has cameos in other sitcom series such as "Modern Family" and "Santa Clarita Diet."

As for "Brooklyn Nine-Nine," many of its fans are eagerly awaiting its return this spring, especially after the cliffhanger ending of the season's winter finale. As previously reported, the final moments of season 4 finale showed Gina (Chelsea Peretti) suddenly getting hit by a bus. Hence, many are wondering if Gina will manage to survive the ordeal.

In a previous interview with The Hollywood Reporter, series executive producer Dan Goor was asked whether or not Gina really died from the accident. His response, however, was cryptic.

"Watch and find out!" the showrunner said, adding: "Again, I think another valid question is: did the bus survive? Either way, audiences will see Chelsea again — she is a force of nature and one of the greatest comic minds out there."

"Brooklyn Nine-Nine" is scheduled to return to Fox for the second half of its fourth season on April 11.