The line that Detective Slaughter says in answer to Castle asking if he will be crushing anyone today "I like to keep my options open" is the same line Adam Baldwin's character Jayne uses in the movie Serenity when Nathan Fillion's character Mal asks why he's bringing grenades along - which makes another Firefly reference in this episode.
Nathan Fillion and Adam Baldwin are reunited in this episode. They previously worked together on Firefly, 10 years earlier. There have been many references to Firefly throughout the series. In the episode, Baldwin's character wears a brown coat given to him by Fillion - Fillion played a 'browncoat' in Firefly.
In an interview with Fillion and Baldwin, Baldwin admitted to having taken the jacket in this episode from wardrobe department and not returning it when filming concluded. Fillion then had to clear it with production since it wasn't going to come back.
The jacket initially worn by Slaughter resembles the one worn by Adam Baldwin's character in his early movie My Bodyguard.
When Castle is showing the video of Slaughter at home, he freezes the image and then says "Mother..." to his Mother. However, Adam Baldwin played Animal Mother in "Full Metal Jacket" and this is a reference to this.