Second episode this season in which Stana Katic doesn't appear. Unlike "Cool Boys (2015)", in which it's mentioned that Beckett is out of town, there is no storyline explanation for her absence.
When Castle bumps into Courtney Ford and they discuss the movies based on Nikki Heat, Castle tells to her pass on a "hi" to 'Brandon' for him. He is referring to Brandon Routh, to whom Ford has been married since 2007.
Mason says Kendall is deadly with a sniper rifle at 1.5 miles. For perspective, only six military snipers have ever had confirmed kills at that range.
This episode has Summer Glau and Doug Savant who starred and guest starred in Bushwhacked (2002) with Nathan Fillion.
Doug Savant and Nathan Fillion have also worked together before on both Desperate Housewives (2004) and Firefly (2002). Another Firefly/Serenity (2005) alum to appear on the show, Summer Glau, played River Tam in Firefly/Serenity.