Production on Season 8 of "Castle" has already commenced and just recently re-signed costar Stana Katic is already expressing excitement over what the new season holds.

According to Enstarz, the 37-year-old newlywed recently shared with fans that she had a great first day back at work and can't wait for the Sept. 21 season premiere.

It's shaping as a season like few others for the long-running drama series with cast regular Molly Quinn recently teasing fans this season of the show will be on steroids.

"Don't be worried," costar Nathan Fillion recently told TVLine of all the rumors his Richard Castle character and Katic's Det. Kate Beckett are headed for a split. "In order for a show to continue and to move forward, things have to change. And things have changed, every year, for these two."

With new series co-show runners Alexi Hawley and Terence Paul Winter now on board, rumors have been running rampant about several new twists the series may take this season.

One of the most talked-about are reports the season will find Castle spending plenty of time with a new female character known as Hayley.

TVLine 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.

The casting of the Hayley character has many wondering what she may come to mean for Castle and Beckett's relationship. Speculation has ranged from her being someone the crew may have encountered during one of their high-pressured cases to someone Beckett may need as part of her inner-circle during her rumored run for New York Senate.

When it comes to plot lines, whatever changes the show might undergo between last season and the upcoming one pale in comparison to all the drama that recently played out in getting the two costars to re-sign deals to return for another season.

Both Katic and 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.