Gideon profiles a killer and correctly predicts that he would have a speech impediment. This was based on a real-life case investigated by FBI agent John Douglas, former chief of the FBI's Investigative Support Unit.
This episode has the most times a different book quote was recited in a single episode, with a total of four, all recited by Gideon.
Lukas Haas originally auditioned for the role of Spencer Reid. He instead got the role of 'The footpath killer' after he began expressing doubt about doing a series.
One of the names that Haley suggests for her and Hotch's child is Gideon, which she may or may not know is the last name of Hotch's colleague Jason Gideon. Mandy Patinkin actually does have a son named Gideon.
"Extreme Aggressor" is a term referring to a strategy type for Go, a heavily strategic yet relatively simple Chinese board game that was played by Richard Slessman. This strategy was pointed out by Reid as a challenging type of strategy due to its rather aggressive nature.