Summary

• Nathan Fillion reunites with Firefly and Castle co-stars on The Rookie, building on long-standing relationships with fellow actors.
• The Rookie offers engaging stories with familiar faces like Alan Tudyk, Sean Maher, and more, bringing nostalgic moments for fans of Fillion's past work.
• The show's cast showcases versatile talents, with Annie Wersching portraying memorable villains and Annie Wersching playing a recurring role.

Nathan Fillion remains one of the more personable Hollywood stars, and there have been nine Firefly and Castle actors on The Rookie, reuniting with the beloved lead star. After a smaller role in Steven Spielberg's Saving Private Ryan and a lead role in the sitcom, Two Guys, a Girl and a Pizza Place with Ryan Reynolds, Fillion enjoyed his breakout role as Captain Malcolm Reynolds in the 2002 series Firefly. The show remains a cult hit, even though Fox canceled it after one season. Fillion found more success on Castle, which aired for eight seasons on ABC.

Since 2018, Fillion has played the main protagonist, The Rookie. The series follows the life of Nolan, the oldest rookie officer in the department, and his fellow officers in the Mid-Wilshire Division. During the Rookie's five seasons, Fillion, who has formed close relationships with his co-workers throughout his TV career, reunited with actors he previously worked with on Firefly and Castle, with nine appearing on The Rookie, as criminals, allies, suspects, and witnesses for the various crimes.

The Rookie is available to stream on Hulu.

9 Alan Tudyk (Firefly)

Tudyk Stars As Crime Scene Cleaner Ellroy Basso

Firefly star Alan Tudyk plays the beloved character Hoban "Wash" Washburn, the ace pilot with a dry sense of humor who flies the Serenity in Firefly. On Firefly, Wash was married to the ship's first mate, Zoë (Gina Torres). While Tudyk never worked with Fillion on Castle, he has made up for it with more than one appearance on The Rookie​​​​​.

Ellroy meets Fillion's Officer Nolan in the season 2 episode, "Clean Cut."

Tudyk, who remains close friends with Nathan Fillion, has appeared in two episodes of The Rookie, playing crime scene cleaner Ellroy Basso. Ellroy meets Fillion's Officer Nolan in the season 2 episode, "Clean Cut." In this episode, some killers show up at the crime scene and fire shots at them. In the season 4 episode "Day in The Hole," Ellroy and new dispatcher girlfriend Nell Forrester (whom Nolan introduced to each other) up with Nolan and his firefighter fiancé Bailey Nune when Nolan is assigned a case at the border.

8 Sean Maher (Firefly)

Maher Played Escaped Convict Caleb Jost

Firefly was the kind and gifted doctor Simon Tam who, along with his sister River, is running from the evil Alliance when they find refuge aboard the Serenity. Simon goes on to work as the ship's doctor as he fights to heal his sister, becoming a fugitive in the process. While Maher never appeared on Castle with Fillion, he did appear in The Rookie in a very surprising role.

In the season 1 episode of The Rookie, "Manhunt," Sean Maher plays another character evading the law

In the season 1 episode of The Rookie, "Manhunt," Sean Maher plays another character evading the law, as escaped convict Caleb Jost. Jost is the complete opposite of Tam in that he is a conniving and dangerous criminal who holds his mother-in-law hostage with a deadly contraption. In the episode, Jost is on a prison bus that crashes, which sees several convicts injured and many others escape. Nolan comes across Jost when he offers to help an FBI hostage negotiator track him down.

7 Gregg Henry (Firefly)

Henry Played A Judge In The Rookie

Veteran actor Gregg Henry stars in the Firefly season one episode, "The Train Job," as Sheriff Bourne of the mining town Paradiso on the planet Regina. Bourne is a benevolent lawman who allows Fillion's Reynolds and the Serenity crew to leave after they return stolen medicine to the town. It was a rare case of a lawman who aided and helped Fillion and his crew.

He only had a brief cameo in The Rookie's season 1 episode, "Homefront"

Henry had a less helpful role in The Rookie. He only had a brief cameo in The Rookie's season 1 episode, "Homefront," as a judge presiding over a lawsuit filed against Nolan for allegedly using "excessive force" during a foot chase, resulting in an injury. The entire plot was done humorously, as Nolan ended up assigned the youngest attorney the union had available to represent him. The Judge, who remains unnamed, lets Nolan off with a warning, saving his future career on the police force.

6 Jon Huertas (Castle)

Huertas Starred As An Undercover Agent On The Rookie

Fillion's Richard Castle often assisted John Huertas' NYPD Detective Javier Esposito on Castle, and Esposito was known to get Castle out of a few scrapes during particularly dangerous cases. Esposito was one of the main characters in Castle, appearing in every season of the show from the start to its explosive finale. He was able to work with Fillion again on The Rookie — in more than one job role.

Huertas first appeared in the season 1 episode of The Rookie, "The Bet"

Huertas first appeared in the season 1 episode of The Rookie, "The Bet," as an undercover agent with the Department of Homeland Security. This is a major part of the episode, as Nolan has to help work on a high-stake criminal case involving Huertas's Alejandro Mejia/Cesar Ojeda. This also marked a big Castle reunion as Seamus Dever also appeared. Huertas later returned to the series for the season 5 episode, "Double Trouble," but this time he was behind the scenes as the episode's director.

5 Seamus Dever (Castle)

Dever Plays A Lawyer Arrested For Buying Drugs

On Castle, Seamus Dever played NYPD Detective Kevin Ryan, the best friend and police partner of Javier Esposito (Jon Huertas). The chemistry between Ryan and Esposito provided a lot of humor in the series, often bickering about each other's lives and occasionally competing with Castle and Beckett on who would first solve a murder case. Things changed when Dever appeared on The Rookie, as he had a much more antagonistic relationship with Nathan Fillion's John Nolan.

Dever also appeared in the season 1 episode of The Rookie, "The Bet"

Dever also appeared in the season 1 episode of The Rookie, "The Bet," in the less noble role when he plays Chaz Bachman, a lawyer Nolan arrests for buying drugs. Sadly, for fans of Castle, Dever and Huertas were in different storylines on the show, and they never had a chance to appear together on the screen. With that said, Dever showed that he could play slimy and arrogant on The Rookie just as well as he could play righteous and upstanding on Castle.

4 Tamala Jones (Castle)

Jones Plays The Mother Of Rookie Police Officer Aaron Thorsen

Tamala Jones' Castle character Dr. Lanie Parish is the NYPD medical examiner, forensics analyst, and girlfriend of NYPD Detective Javier Eposito (Jon Huertas). She regularly provides key clues to help solve cases investigated by Castle and Detective Kate Beckett. She was around for the entire series of Castle, and when she reunited with Nathan Fillion on The Rookie, she took on a very different role than fans were used to.

In the season 4 episode of The Rookie, "End Game," Tamala got an opportunity to play Yvonne Thorsen

In the season 4 episode of The Rookie, "End Game," Tamala got an opportunity to play Yvonne Thorsen, the mother of rookie police officer Aaron Thorsen. As a manipulative parent (and wife of a former rap star) who sees dollar signs and high reality TV ratings in her son's police career, Yvonne is the opposite of the caring and clever mystery solver Lanie. She later appeared in the episode "Real Crime," where a reality show was filming at her mansion when a dead body was found.

3 Molly C. Quinn (Castle)

Quinn Plays A Young Woman Who Is Arrested For A Kidnapping Con

One of the most important aspects of Castle was the close parent and child-relationship between Richard Castle and his daughter Alexis, who both had open and honest dialogue that was grounded in unconditional trust and love. Fans watched her grow up on Castle, starting out as a teenager in the first season and ending the show in her early 20s. That dynamic was revisited when Alexis actress, Molly C. Quinn, appeared in two episodes of The Rookie as Ashley.

Molly C. Quinn, appeared in two episodes of The Rookie as Ashley.

Ashley is the illegitimate daughter of felon Oscar Hutchinson. In the season 3 episode, "Bad Blood," she was arrested for a kidnapping con on her boyfriend's parents, which she itted to when she met her father for the first time. In an episode from season 5, "Death Notice," Ashley gets out of prison for her part in the con, and she and Nolan share a poignant scene where she seeks advice when she suffers a kidney infection and her father offers her a kidney, but only if she pays him monthly for it

2 Toks Olagundoye (Castle)

Castle's P.I. Partner: Toks Olagundoye Suits Up

Toks Olagundoye's Hayley Shipton, a fan-favorite character on Castle, was an adventurous private investigator and former police officer who helped Castle uncover secrets from his past. Hayley also assisted both Castle and Alexis with their own cases, often using unapproved methods. She was a late addition to the show, making her debut in the season 8 premiere, but quickly became a fan favorite as she worked with Castle's PI agency.

For The Rookie, Olagundoye appeared in six episodes of season 3

For The Rookie, Olagundoye appeared in six episodes of season 3 as Fiona Ryan, an Ethics and Criminal Justice professor who teaches the night class that Nolan attends as part of the rookie process to become a T.O. Fiona Ryan was a mentor for Nolan, as he spoke to her at length about his concerns about professional ethics when it came to civil rights. Ryan also goes to Nolan for help when someone starts stalking her in "New Blood." Her final appearance was in the season 3 finale, "Threshold."

1 Annie Wersching (Castle)

Castle's Villainous Doctor: Annie Wersching Makes Her Mark

Annie Wersching delivered chilling, unforgettable roles on both Castle and The Rookie. In Castle, Wershing portrayed Dr. Kelly Nieman, a renowned cosmetic surgeon and girlfriend of the serial killer, Jerry Tyson (3XK), who obstructed Castle and Beckett's murder investigation. She appeared in three episodes as she helped Tyson remain hidden and become an accomplice in "Disciple," "Resurrection," and "Reckoning." Her obsession with Beckett makes her a memorable villain.

Wersching played a recurring villain on The Rookie

Wersching played a recurring villain on The Rookie, Rosalind Dyer, a maniacal serial killer obsessed with Nolan and the officers and detectives of Mid-Wilshire. The death of Rosalind in season 5 is ranked as one of the most upsetting deaths in The Rookie as Nolan tries to save her only for a sniper to gun her down. Sadly, audiences will never have a chance to see new performances from the brilliant Wersching, as the actor died in January 2023 from cancer.