The younger Hotchner brother, Sean, is introduced. Despite apparently seeing each other on holidays, and residing nearby, this is Sean's first, and only (known) visit, to Hotch's office. Furthermore, most of the team didn't even know he existed.
Eric Johnson is featured as Hotch's brother, Sean. Johnson would later go on to star in Fifty Shades Darker (2017) The song "The Scientist" was featured in both this episode and that film.
Gregory Cruz (John Blackwolf) and Chad Allen (Jackson Cally) previously worked together on Dr. Quinn, Medicine Woman (1993).
When Blackwolf says 21 feet, Hotch's face shows that he knew what Blackwolf was taking about before Reid asked.