When Beckett calls Castle to tell him about the favor Rogan wants from her in exchange for signing the divorce papers, Castle's "Captain Castle" nameplate from "That '70s Show (2014)" is visible on his desk.
Rogan makes a reference to a college aged Beckett picking the lock on Pearl Jam's tour bus to steal Eddie Vedder's jean jacket. Eddie Vedder's music has been featured on several episodes of Castle.
The leader of the biker gang has been on Castle before. In the episode "Almost Famous" (2010) he can be seen in a photograph shown on one of the shows the victim had worked on.
You can see the skateboard Ross De Koning (Blake Cooper Griffin) hands Castle at the end of "Law and Boarder" hanging on the wall of Castle's office.
The past marriage problem is similar to The Thanksgiving Decoupling (2013), and is very similar to different story lines in Friends (1994).