Nathan Fillion recently assured everyone all will be fine during Season 8 between him and series co-star Stana Katic.

With the show having new showrunners this season and several plot changes in store, many have wondered what that might mean for the union of Castle and Beckett.

"Don't be worried," a smiling Fillion recently told TV Line while stopping by the website's Comic-Con interview suite. "In order for a show to continue and to move forward, things have to change. And things have changed, every year, for these two."

Rumors have run rampant that the new season will find Castle spending plenty of time with a character known as Hayley.

TV Line previously reported show executives recently held auditions for the role, describing the character as "a quick-witted, free-spirited former LAPD cop" who now works as a security specialist. Specifically, ABC execs are rumored to be eyeing either a black or Latina actress for the role of the 20-something character.

Aside from all the questions about Castle and Beckett's relationship, viewers are probably also wondering why the cast would need a security expert. Speculation has ranged from her being someone the crew may have encountered during one of their high-pressured cases to her being someone Beckett may need as part of her inner-circle during her rumored run for New York Senate.

Whatever changes the show might undergo between last season and the upcoming one surely pale in comparison to what could have been if execs did not move in the 11th hour to bring back Katic in the role of Beckett.

Both Katic and Nathan Fillion's contracts expired at the end of the season, and network officials were only recently able to reach terms on a new deal with Katic.

While stressing they have a Plan B in place, new co-showrunner Alexi Hawley admitted to TV Line the show would have been "fundamentally different" without Katic.

Hawley is slated to share showrunner duties next season with Terence Paul Winter.