The establishing shot of the RMS Bentley is of the former RMS Queen Mary now the Queen Mary Hotel in Long Beach, California. The photo was modified to remove a WWII submarine from the foreground and add a NYC skyline to the background.
In the show's eight seasons, this is Castle (2009)'s first mid-season finale. Along with Nashville (2012), it was one of the last prime time ABC series on the air at the time to adopt the two-part season format.
Nathan Fillion and Kristoffer Polaha both auditioned for roles on Buffy the Vampire Slayer (1997); though he was later cast as Caleb in season seven, Fillion originally auditioned for the role of Angel, and Polaha auditioned for the part of Riley Finn in season four.