The "Castle" cast for Season 6 is still growing.

A rep for ABC has confirmed that Joshua Bitton has will have a multi-episode arc in Season 6 as Grant “Sully” Sullivan, a new detective trying to prove himself at the 12th Precinct, as first reported by TVLine.

Bitton, who's appeared on "Private Practice," "Justified" and many more primetime hits, joins a long list of new faces in the expanding "Castle" cast: Former soap star Antonio Sabato Jr. will play Ramon Russo, an actor best known for his role on the fictional "Saved By The Bell"-esque '90s sitcom "2 Cool For School"; Yancey Arias will appear in the first two episodes of Season 6 as Carl Villante, the head of an elite investigative unit who butts heads with both Beckett (Stana Katic) and Castle (Nathan Fillion); "24" alum Glenn Morshower will play Michael Reed, a former general who's determined to protect the secrets of his past in Episode 2; "Alphas" alum Warren Christie is also set to appear in Episode 2 as reporter Brad Parker; and "House" alumna Lisa Edelstein will have a multi-episode arc on "Castle's" upcoming sixth season as Rachel McCord, "a tough and highly-skilled Federal Investigator whose appearance plays a vital role in Beckett’s decisions about her future," according to TVLine.

"Castle" Season 6 premieres on Monday, Sept. 23 at 10 p.m. ET on ABC.

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