The universe of ABC’s weekly whodunit is about to get a lot more confusing. See if you can follow: in Castle, Nathan Fillion (Firefly, Serenity) plays a millionaire crime novelist akin to James Patterson, who follows NYPD detective Kate Beckett (played by Stana Katic) in order to get inspiration for his series of novels.

The characters of the novels mirror Castle and Beckett’s ‘real’ relationship.

TV Guide reports that Laura Prepon, best known for her role as Donna in That 70s Show, will play an actress hired for the movie role of Nikki Heat, Beckett’s literary counterpart. In addition, Prepon’s actress-character, Natalie Gray, will tail Castle and Beckett for inspiration of her own.

So, Prepon is a real actress, playing a fictional actress, playing a fictional role, based on a fictional novel, based on a ‘real’ fictional cop. Except that the books Castle writes aren’t entirely fictitious (even if they are fictional), ABC has hired ghost writers and published the books that Fillion’s character writes – which you can buy in a real bookstore.

By contrast, the news about Melrose Place veteran Thomas Calabro is pretty straightforward. Calabro will a murder suspect in an investigation surrounding a matchmaker for high-class Manhattanites.

Both Calabro and Prepon have played relatively minor roles since their breakouts. Prepon had a lead role ABC’s short-lived October Road and Calabro reprised his role of Dr. Mancini in CW’s revival of Melrose – which fizzled out after just nine episodes earlier this year.

Castle has found a good niche as light hearted murder-mystery among more serious fare like Law & Order: SVU and TNT’s The Closer.

Nathan Fillion’s status as an underground sci-fi star has helped the show along considerably. After Buffy and Firefly, he’s made the rounds on geek-favorite shows such as Justice League Unlimited, Robot Chicken, and The Venture Brothers as well as roles in Slither, Whedon pet project Dr. Horrible, and the recent Wonder Woman direct-to-video movie.

Fillion and co-star Stana Katic have excellent chemistry in a flirty arc that’s been building since the series began. Screen Rant readers may recognize Katic from the latest Librarian TV movie and a brief recurring role in the 5th season of 24.

Both Laura Prepon and Thomas Calabro are set to appear in the January 3rd episode; though, Prepon’s role may continue for a few episodes more.

Castle airs Monday nights at 10pm on ABC.

Source: TV Guide