archive footage used for flashbacks
Both the source novel and Hitchcock's film are mentioned by Castle in relation to the episode's two murder cases, before offering his own alternate title of "Strangers On A Boat".
Mentioned by Castle.
Castle: "...more like Six Degrees Of Kevin Bacon."
A suspect asks if he's "being Punk'd".
Castle refers to a clownfish as Nemo.
After Ryan mentions the movie in connection with their current case, Esposito says "Crash is overrated".