Nathan Fillion’s ‘Castle’ Co-Star Was Shocked by How Much He Changed in ‘The Rookie’

Actor Nathan Fillion has worked with a few notable guest stars during his time with The Rookie cast. But there was one guest star who he surprised with his new attitude.

This former ‘Castle’ star was shocked by how much Nathan Fillion changed on ‘The Rookie’

Fillion has been a part of some of television’s most critically praised shows. Before The Rookie, he was known for playing millionaire author Richard Castle in the titular series Castle. Many of Fillion’s former Castle co-stars have made small appearances on The Rookie, from Jon Huertas to Tamala Jones. 

Jones, who played a medical examiner on the hit series, portrayed a wife to a former rap star on The Rookie. She was more than excited to team up with her former Castle co-star. But she was surprised at Fillion’s newfound maturity on set.

“That was so great. But I was a little shocked because when Nathan was Castle, he was full of pranks. I didn’t get pranked at all on The Rookie; I was waiting on it, but it didn’t happen. So I think he’s matured since Castle,” she once told Screen Rant.

Castle and The Rookie weren’t the only hit shows that Fillion starred in. Years prior, he was a part of another cult favorite television show with the sci-fi series Firefly. 

Fillion starred with many familiar actors like Alan Tudyk and Gina Torres on the show. He once caught up with these two stars in a virtual event hosted by Rookie creator Alexi Hawley.

During the conversation, Torres was asked about perhaps guest-starring on The Rookie. She confided that she would, but only on one condition. Torres had already guest-starred on Fillion’s Castle. The only problem was that she didn’t get to work with Fillion on the episode, an experience she didn’t want to relive.

“You’ll have to promise you’ll actually be there because when I came on Castle, you bailed,” Torres told Fillion, according to Entertainment Weekly.

Hawley, however, reassured that Torres wouldn’t need to worry about the same thing happening on The Rookie.

“There’s no way I’d bring you on the show and not write you into Nathan’s story,” he said.

Why it’s unlikely that Nathan Fillion’s ‘Castle’ co-star Stana Katic might ever do ‘The Rookie’

Stana Katic was one Castle star who has yet to appear on The Rookie. As Fillion’s love interest and partner officer Kate Beckett, she was once the show’s most important character behind Castle himself. But she was fired during the show’s eighth season, a decision that shocked many.

There were rumors that Katic and Fillion might not have gotten along behind the scenes. Their feud was never corroborated, but Katic once opened up about the situation during an Entertainment Weekly interview.

“I’m actually still not clear on the thought process behind the way that it went down. It hurt and it was a harsh ending, but now, nearly two years later…I met so many beautiful people on that project, and we collaborated on something really unique in that it’s not every day that you get a show, or a series, that has eight seasons and that it was a hit for the network,” she said.

But she chose not to air any dirty laundry due to her gratitude for working on the show, and the connections she formed.

“It was a formative experience, and we told a love story that I feel moved people, touched people, and I can’t be anything but glad that I was a part of something like that. I hope it remains something special in viewers’ minds forever,” she added.

Given that Katic and Fillion didn’t part ways amicably, it may explain why Katic hasn’t appeared in the series yet.

Nathan Fillion thought that he would dislike this ‘Rookie’ co-star

Saturday Night Live alum Pete Davidson once had a guest spot on The Rookie. He portrayed Fillion’s half-brother, who was less law-abiding than Fillion’s John Nolan character. The two first met when they did James Gunn’s The Suicide Squad. Recently, Fillion admitted that he had some preconceived notions about Davidson. 

“When I first met him, I thought, ‘He and I are probably not going to be best pals.’ And within four minutes, I was embarrassed and ashamed because I’d judged a book by its cover,” Fillion said on The Hollywood Reporter.

It turned out that Davidson was the complete opposite of who Fillion thought he was.

“He’s an incredibly kind man. Within two or three days, I invited him to do an episode, and he graciously accepted. He’s wildly talented and always brings a flavor to the character that’s realistic. It’s been a pleasure seeing what this unlikely friend of mine can do with being an unlikely half-brother and friend to my character,” Fillion said.