Nathan Fillion and Stana Katic React to 'Castle' Cancellation

All things must end," Fillion tweeted. "It has been an honor."

— -- Nathan Fillion and Stana Katic spoke out today about the cancellation of "Castle."

Both expressed their gratitude to the fans and their colleagues for their support over the past eight seasons.

Fillion also joked about seeking new work, writing a note to "every director," saying, "It appears I have an opening in my schedule," and to fans, asking them to praise his talent.

"All things must end," he wrote of his time on the ABC drama. "It has been an honor working with the men and women of 'Castle.' I am truly amazed at what we've done. Thank you all."

Katic also shared a handwritten note, addressed to "Castle" fans, cast and crew.

"Your devotion to our show has carried us for these unforgettable 8 seasons," she wrote. "I'm lucky to have met and worked with and for the lot of you. I will always be grateful."

"Castle" was about a mystery novelist, played by Fillion, who teamed up with an NYPD homicide detective (Katic) to solve crimes. It premiered in 2009.

Earlier this year, ABC announced that Katic would not be returning to "Castle" after this season.