When Castle and Beckett are trying to shorten their list of wedding guests, he wants to cut her aunt Teresa because of something, which is implied to be disparaging, she posted about him on Facebook, and Beckett replies that it was eventually taken down. While on the phone with her dad in "Limelight (2014)", Beckett learns of whatever Teresa wrote and tells him to pass on a message to take it down.
The investing banking firm in the episode is called J.P. Harding and is a thinly veiled reference to J.P. Morgan. The character of Jamie Burman is the CEO of this fictional company to align to Jamie Dimon, the CEO of J.P. Morgan.
At the beginning of the episode, Castle expresses his desire to get married on the Cyclone, a roller coaster at Coney Island. During their investigation in "Deep Cover (2014)", it's revealed that a spot under the Cyclone is the primary crime scene where the victim was murdered.