Black and Tan: A Crime of Fashion - S2-E15
Factual error: In the flashback at the beginning of the episode, Shawn is wearing a Knight Rider T-shirt. This flashback takes place in the 80's, but the art printed on the T-shirt is a picture-perfect copy of the cover art from the US DVD release of Knight Rider Season 3 - this DVD set (and the cover art style/arrangement) was not released until 2006: http://en.wikipedia.org/wiki/Knight_Rider_%28season_3%29.
Extradition: British Columbia - S4-E1
Continuity mistake: When Shawn flashes back to remember where he has seen Pierre Desperaux, he flashes on a photo of Pierre in Lassie's apartment next to Ernesto Chavez (on the right) on Lassie's wall. Going back to Season 3, Episode 11, when in Lassie's apartment, there is no photo next to Ernesto's photo. (00:03:20)
Visible crew/equipment: When Dwayne Tancana is about to jump off the boat, his mic gear is seen tucked in his belt. (00:21:00)
Continuity mistake: Just before Gus is awoken by noises in his apartment, there is a shot of his alarm clock. The time shows 6:07PM. When he gets out of bed, the clock says 7:01 (cannot determine if it is AM or PM). Even assuming he just lay in bed for an extra hour, he then tracks down Lassie who is about to eat lunch. (00:27:00)
Woman Seeking Dead Husband - Smokers Okay, No Pets - S1-E4
Continuity mistake: When the bank robber enters the mausoleum, his hands are empty. When Raylene points her gun at everyone, he raises empty hands. After Lassie and Juliet arrest David and Raylene, the bank robber is holding a slushie cup. (00:36:40 - 00:37:30)
Six Feet Under the Sea - S3-E10
Continuity mistake: When Shawn and Gus are driving the boat at night, we see the coordinates on the GPS tracker - two seconds later (real time, as they are talking), the coordinates have changed; now they are about 37 miles from where they were, so they must have hit 65,000 mph for those 2 seconds. In case my math needs correcting, the first set is 34 06' 50.25" N x 120 17' 41.31" W and the second set is 33 57' 40.21" N x 119 35' 56.58" W. (00:21:55)
From the Earth to Starbucks - S1-E10
Continuity mistake: As Shawn and Gus walk up the stairs to the courthouse, there are only two men standing beside the steps, at the fence. The camera angle changes and there are three completely different people standing there. (00:01:15)
Other mistake: After they trace the number from the vampire bar they bring Marla's roommate in for questioning. Calling a bar, that has zero connection to the murder, and asking for blood wouldn't make someone a suspect or be enough to bring them in for questioning.
Character mistake: When Shawn looks at Curtis Stanzen's file in Leo Quinn's office, guilty is misspelled. It says "gulity". (01:30:00)
Extradition: British Columbia - S4-E1
Character mistake: When Shawn is checking Ed's book of valuables, the crown that Shawn thinks Despereaux will steal, has a listed value of "950,000 - 1,000,00,000 USD." I guess it's really, really(!) valuable, enough that a whole new numbering system was made up for it. (00:30:55)
He Loves Me, He Loves Me Not, He Loves Me, Oops He's Dead - S1-E11
Continuity mistake: When Shawn and Gus are back at the office after the sorority ghost sighting, Gus talks to Sean from his desk. Shawn is just on Gus' right and Gus' head is turned slightly towards him. The camera angle changes and Gus is turned left (Shawn has not moved). Then Gus is again looking left. (00:16:40)
Continuity mistake: When Shawn sees the box with the dead doctor's files, Regina Kane's file is visible halfway back in the box. He then tells Gus, "All we have to do is find Regina's." (Which he was looking straight at, but let's call that a character mistake.) A few moments later, we cut back to Shawn and Gus and Shawn finds her file in the front of the box. (00:37:00 - 00:37:40)
Chosen answer: "Psych: The Musical" was supposed to air during the regular season 7 schedule, before Chief Vick is suspended and Jules discovers Shawn's lie, but the network decided to push it back to air as a special episode, sort of as a tie in with the holiday season and a lead in to season 8, which was to begin only a couple of months later.