TRIVIA: As a running gag, in every episode you'll find a pineapple, the word "delicious," a fist bump, the phrase, "I can't do this right now," and the question "What?"
James Roday (Shawn Spencer) and Maggie Lawson (Juliet O'Hara) started dating during the filming of season one. Their relationship lasted seven years.
Inspired by how Series Creator Steve Franks' father, who was a Los Angeles Police officer, would teach him how to be observant.
With the exception of Emilio Estevez who appeared in name only as one of Shawn's aliases, and Paul Gleason, every main actor and actress from The Breakfast Club (1985) appeared in the series. Judd Nelson appeared in the episode "Death is in the Air", Molly Ringwald appeared in the episode "Shawn Interrupted", Ally Sheedy appeared in the episodes involving the Yin-Yang killer and "Psych: The Musical", Anthony Michael Hall appeared in "No Trout About It" and the beginning of season eight, and John Kapelos appeared in two episodes ("Santa Barbarian Candidate" and "1967: A Psych Odyssey").
A recurring gag featured in the show's outtakes involves the cast and crew laughing hysterically at the mention of the phrase "three-hole punch." According to James Roday, the gag began with a script written by Tim Meltreger, which included a joke about a three-hole punch. During filming, Roday misspoke the line as "three-hole puncher." Meltreger called for a cut and raced onto the set, then insisted that Roday read the line exactly as scripted, because, in his words, "Three-hole punch is *way* funnier than three-hole puncher!" Subsequently, it became a running joke on the set: someone says the words "three-hole punch" while shooting and the cast and crew all pretend to laugh as if it's the funniest thing they've ever heard.
Spencer's mother, played by Cybill Shepherd, is called Madeleine, as a nod for her character in show Moonlighting (1985), Madeleine (Maddie) Hayes.
A running gag in the show is that Gus and Shawn will frequently say "C'mon son!" when something strange, surprising, or silly has happened. This phrase was coined by media personality Ed Lover. In the season eight episode "Remake, a.k.a. Cloudy...With a Chance of Improvement", Ed Lover guest starred as a bailiff, telling Gus to "Come on, son" as he attempts to escort him from the courtroom. He also appeared in the season six episode "Last Night Gus" as himself.
In season six, episode four (The Amazing Psych Man & Tap Man, Issue #2), Juliet acts impressed thinking that Shawn is The Mantis. She immediately learns that Shawn is faking it and Shawn responds with the phrase "I know you know that I'm not telling the truth...... I know, you know," which are the exact lyrics of the Psych theme song.