Smallville's Justin Hartley will guest-star on Castle, TVLine reports.
The actor will play the boyfriend of Kay Cappuccio (guest star Hilarie Burton), a Kim Kardashian-like reality star who's famous for being famous. No word yet on if they get married for 72 days.
Keck's Exclusives: Hilarie Burton gets the keys to the Castle
Hartley most recently appeared on Chuck
returns Monday, Dec. 5. Hartley and Burton's episode, titled "An Embarrassment of Bitches," will air early next year.