Kirsten Nelson was pregnant in real life when she auditioned for her role as Interim Chief Karen Vick. During the first few episodes, she gave birth; from that time on she had to wear a fake pregnant stomach for the remainder of her character's pregnant period, to compensate for her diminishing belly.
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.
Shawn and Gus almost always wear opposing shirt patterns (between plaid and striped). Shawn almost always wears short sleeves, while Gus rolls his sleeves to three-quarters. Even in episodes where they are wearing sweaters, the undershirts will alternate. In some episodes, Gus will wear a pinstriped suit while Shawn wears a plaid shirt.
Gus always uses Microsoft-related products while Shawn always uses Apple-related products. This includes their phones in later seasons where Gus can be seen using a Windows phone (e.g. s7e6 "Cirque Du Soul"), and it's well-known that Shawn uses an iPhone. Gus always uses a PC, and Shawn uses a Mac. Except for in some episodes where an Alienware laptop can be seen on Shawn's desk. This can clearly be seen in the episode "Forget Me Not".
According to his "MySpace" page, the following is a list of jobs that Shawn Spencer held before becoming the CEO of Psych: Newport Sailing Assoc., Newport Beach, CA US Assistant Race Chair 2006; English, Inc. Kho Samui, TH Teacher, TEFL 2005; Comerica Park Detroit, MI US Concessions Vendor 2005; Apollo Agency Seattle, WA US Foot and Ankle Model 2005; Ben and Jerry's Burlington , VT US Customer Service 2004; Minute Maid Park Houston, TX US Concessions Vendor 2004; Aquablanca Expeditions San Jose, CR Raft Guide 2003 - 2004; U.S. Cellular Field Chicago, IL US Concessions Vendor 2003; Flynn Special Events Santa Barbara, CA US Event Planner 2003; Mo's Outdoor Decor Santa Barbara, CA US Christmas Light Hanger 2002; Graceland By Night, Inc. Memphis, TN US Tour Guide 2002; Miller Park Milwaukee, WI US Concessions Vendor 2002; Oscar Meyer Wienermobile Madison, WI US Driver 2001 - 2002; Safeco Field Seattle, WA US Concessions Vendor 2001; Feedback, Inc. Santa Barbara, CA US Mystery Shopper 2000 - 2001; Turner Field Atlanta, GA US Concessions Vendor 2000; Assemblyman Skip Warner El Paso, TX US Constituent Relations 1999; Camp Durango Silverton, CO US Water Ski Instructor 1998 - 1999; Barrett's Mardi Gras Universe Algiers, LA US Construction 1997 - 1998; Hampton Inn Austin, TX US Desk Clerk 1995 - 1996; Pacific Emerald Cruise Lines San Pedro, CA US Lifeguard 1994 - 1995. During one episode he mentions having worked at Meineke for 2 afternoons.
The casting team for this show appears to have a marked love of 80's TV shows and movies. They've cast stars from TV shows Growing Pains, Family Ties, Family Matters, Cosby Show, Moonlighting, Married With Children, Good Times; and movies Breakfast Club*, Star Trek, Ferris Beuller's Day Off, Princess Bride, Pretty in Pink, Rocky Horror Picture Show, Ghostbusters, La Bamba, and Revenge of the Nerds. This is FAR from a complete list. 4 of the 5 students in Breakfast Club have appeared on Psych. The only one not cast is Emilio Estevez, although Shawn uses this name as a cover while investigating in the season 3 episode, "Any Given Night at 10PM, 9PM Central" (3.13) as well as the later season 8 episode, "Someone's Got a Woody" (8.04).
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 8 episode "Remake A.K.A. Cloudy... With a Chance of Improvement", Ed Lover guest stars as a bailiff, telling Gus to "come on, son" as he attempts to escort him from the court room. He also appeared in season 6 episode "Last Night Gus" as himself.
With the exception of Emilio Estevez every main character from The Breakfast Club (1985) appeared in the series. Judd Nelson appears in episode "Death is in the Air", Molly Ringwald appears in episode "Shawn Interrupted", Ally Sheedy appears in episodes involving the Yin Yang killer and "Psych: The Musical", Anthony Michael Hall appears in "No Trout About It" and the beginning of season 8. Even supporting character Carl the Janitor played by John Kapelos appears in two episodes ("Santa Barbarian Candidate" and "1967: A Psych Odyssey")
In the final episode, Gus calls his new boss, Mr. Richmond (played by Deon Richmond) "Bud". This was a nod to the character Richmond played on The Cosby Show: Kenny aka Bud. This is also the culmination of a running gag in which Shawn tells people that Gus played Bud.
Several Psych cast and crew members have crossed paths before. Tim Matheson, Freddie Prinze, Jr., Carlos Jacott, Elden Hensen, Tamara Mello, Rachael Leigh Cook, and our own Dulè Hill appear together in the movie, "She's All That". Anna Paquin, Gabrielle Union, and Paul Walker are also mentioned, but don't make appearances.
In this show, the character Carlton Lassiter, played by Timothy Omundson, is named after 2 memorable characters from different 90's TV comedy series. The first one is Carlton Banks, played by Alfonso Ribeiro in "The Fresh Prince of Bel-Air". The second one is Paul Lassiter, played by Richard Kind in "Spin City".
In the episode "Feet Don't Kill Me Now" (5.02), Burton Guster teaches Detective Carlton Lassiter how to tap dance. Lassiter is played by Timothy Omundson, who previously played a tapdancing evil leprechaun Seamus McTiernan in the 2001 Disney TV movie "Luck of the Irish".
Family Guy nods to this show in S8: E12, when Peter pretends to be psychic and helps the police force solve a crime. This is the whole basis of "Psych" and Peter even says he will psych out the criminal, which is a line in the "Psych" theme song
The trivia items below may give away important plot points.
In the final episode, "The Break-Up", Chief Vick and Juilet mention that they can't hire Psych as a consulting team because they already have a guy and he is "alphabetizing the pantry as we speak". This is a reference to the television show Monk, which is set in San Francisco.
A running gag in the show are that Lassiter constantly metions a "Detective Dobson", but we never see him. Another running gag is that Shawn is told he looks like actor Val Kilmer. On the season finale, Detective Dobson is shown, and he is played by none other than Val Kilmer.
In the pilot Shawn tells Gus that he will never tell anyone that he's not psychic. Throughout the series he never does completely admit it to anyone besides Juliet O'Hara who discovered it by herself in Deez Nups. The closest he gets to telling anyone is in the finale on his video to Lassiter, who stops and destroys the disc before Shawn finishes his admission.
4 out of the 5 Breakfast Club members. In the episode "Someone's Got a Woody", Shawn used the final Breakfast Club member (Emilio Estavez) as a nickname to get into a halfway house for an investigation.
In the final episode, Shawn goes up to San fransico to follow Juilet, he mentions that he can work up there for the SFPD and chief Vic say they already have a guy and he is pretty good and that he is in the kitchen rearging the cereal boxes, this was a nod to MONK an old show that had an OCD detective and was aired on USA that ended around the time Psych started
In season 7 episode 1, "Santabarbaratown 2" when the FBI agent is at the police station, Shawn says to him, "I don't get your peachy, Anthony Michael Hall-ish face! What is with his face?" Anthony Michael Hall plays Harris Trout, interim chief of police in season 8.