While looking at the treasure map, Shawn and Gus say "They were digging in the wrong place!" at the same time, referencing the scene in Raiders of the Lost Ark (1981) in which Indy and Sallah also say the same thing at the same time.
Throughout the run of "Psych," people confuse Gus with Deon Richmond, the actor who played Bud on "The Cosby Show." Richmond appears in this episode as Gus's new boss.