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.
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
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.
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.