Trivia: Castle's Halloween costume is of Malcolm Reynolds, played by Nathan Fillion in the short-lived TV show "Firefly." Alexis asks him: "Didn't you wear that like five years ago?" Serenity, the film based on Firefly, was released 5 years before this episode aired.
Trivia: In 2014, the series creators and network were sued for emotional distress by the family of a man named Andy Abarca. Abarca had been killed in a shooting, and actual photos from his autopsy were used in the opening credits montage of the show, evidently without any permission from his family. His mother and sister just happened to stumble across the show on one night in 2013 and were greeted with grisly images of their deceased relative. It was evidently allowed as autopsy photos are considered public documents. As of 2018, there have been no updates on the case.
Trivia: Bradley Walsh had never seen the original American series before being offered his role.