The cast of Breakfast Club, including (L-R) John Kapelos, Judd Nelson, Molly Ringwald, Ally Sheedy, Anthony Michael Hall, and Emilio Estevez. All of these actors appeared in Psych except Emilio Estevez.
In "Shawn, Interrupted," Season 6, Episode 6, Molly Ringwald plays Lavender McElroy, a nurse at a psychiatric hospital which has Bernie Bethel, who is accused of killing his wife, as a patient. While Shawn (posing as a patient) and Gus (posing as a janitor) were in the hospital working undercover, they discover that Lavender was in cahoots with the episode's true villain, Daniel Bethel, Bernie's brother. Lavender was paid by Daniel to tamper with Bernie's medication, therefore keeping Bernie insane.
In "Death is in the Air," Season 4, Episode 13, Judd Nelson plays Dr. Steven Reidman, a CDC doctor who works with Shawn and Gus to contain the Thornburg virus, a fictional deadly virus that causes several deaths."
Ally Sheedy plays Mr. Yang in several episodes: "An Evening with Mr. Yang," "Mr. Yin Presents . . .", and "Yang 3 in 2D." Mr. Yang is a serial killer who supposedly murdered her first victim in 1995. Her counterpart and former partner is Mr. Yin. That year, she was said to have killed six people after a game of cat-and-mouse with each of them. Over the next 14 years, she was to also kill two others and was still not caught, nor her identity revealed. She met Shawn when he was about nine years old and grew attached to him.
In 2013, Anthony Michael Hall appeared on Psych as Harris Trout, an efficiency expert temporarily appointed to oversee the Santa Barbara Police Department.
John Kapelos plays Tom Swagerty in Season 7 Episode10 "Santa Barbarian Candidate" as the Head of the Santa Barbara City Council. He becomes an early suspect when the death of the former mayor, but in the end Tom is not a murderer, merely a professional politician.
He reappears in Season 8 Episode 6 "1967: A Psych Odyssey" asking for a 47-year old missing persons case be solved. The diligence with which Lassiter pursues this long-cold case causes Swagerty to eventually pick him as the new Chief of Police.
Season 3, Episode 2
Gus: Dear Leland Bosseigh High Administrative Board, We accept that you’re withholding our deposit of $1,500 for damages. We also accept that you just see us as you want to see us: in the simplest terms. In the most convenient definitions. A snarky psychic. An uptight pharmaceutical salesman. A pretty female blonde detective. And a not-so-pretty, unusually lanky detective. But each of us is all those things. Plus, our normal fee for solving a murder in one meaningful evening is twice that. So enclosed is a bill for $3,000. Please remit payment in the form of a check made out simply to Psych.
According to Andrew Jeffk, Psych references 471 movies or shows. Among them are Sixteen Candles (pictured here), The Princess Bride, The Shawshank Redemption, West Side Story, Jaws, Smokey and the Bandit, Ghostbusters, Star Trek, The Lion King, Grease, The Twilight Zone, Rocky, CHiPs, The Shining, Revenge of the Nerds, The Usual Suspects, Psycho, Of Mice and Men, Anaconda, and Miami Vice.