When a ballerina is killed, things get more complicated when ninjas get involved, much to Castle's joy.
- All Asians Know Martial Arts: Subverted. The Green Dragon is a badass martial artist and a middle-aged white American.
- Asian Speekee Engrish: There's a wide variety of Asian characters, some Asian-Americans with natural American accents, some immigrants or businessmen with heavier accents.
- Awful Wedded Life: Beckett hears from her friend Carly about how boring her life is now that she's married, and she worries about the same thing happening to her and Castle. They ended up agreeing to write in their vows to never let their wedded life be so boring.
- Breather Episode: After the heavy episode centered on the Brackenn arc, this is a sillier episode about ninjas.
- Donut Mess with a Cop: Beckett arrives at work one morning to find Ryan and Esposito have bought cronuts from a bakery involved in the case...she promptly takes two.
- Forceful Kiss: The hostess serving Castle kisses him in order not to draw attention to themselves as he quizzes her about the victim.
- Gratuitous Ninja: The killer steals the suspected murder weapon from Castle's hand in a surprise attack, dressed in ninja garb and accompanied by a puff of smoke.
- Two competing ninjas later attack Castle, Ryan and Esposito as they are thrown out of a hostess club.
- The final showdown before the denouement is between two people dressed as ninjas; Bedford, the Green Dragon, and Saya.
- Mistaken Ethnicity: Castle assumes a suspect he and Beckett are interviewing is Japanese (due to the ninjas involved in the case), when he is in fact Korean and takes offense to the assumption.Suspect: Way to racially profile.
- Oh, Crap!: Castle when he accidentally throws a shuriken at Gates.
- Shout-Out: Beckett mentions The Last of the Mohicans and Castle references the 1984 movie Ninja 3: The Domination.
- Truth in Television: The Green Dragon Cult and Black Dragon Society are different organizations from real life history. They're the subject of multiple conspiracy theories (especially the Green Dragons who never really existed) due to their association both with far right wing movements and wealthy backers (the Black Dragons) in much of their history. Though the Black Dragons actually did try to expand power throughout the world and had connections with prominent figures, but also turned to criminal activities and were officially disbanded. While they existed, though, they did try to spread their influence by recruiting young men through martial arts studios.
- Stock Ninja Weaponry: A ninja buries a shuriken into Castle's phone as he is about to call Beckett.
- You Killed My Father: Jade and her sister, Saya, were tracking down a criminal known as the Green Dragon, the person responsible for killing their family.
