Other mistake: In this episode, Shawn supposedly impresses Jules at their first meeting by "divining" facts about her family and cats. We never hear about the cats again and later learn that her parents have not been together for 30 years.
Other mistake: When Spencer is on the phone to O'Hara, his iPhone shows the standby screen, not the screen that comes up when you're talking to someone on the phone.
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.
The Amazing Psych-Man & Tap Man, Issue No. 2 - S6-E4
Other mistake: Before the first break when the scene morphs into a comic of the scene that just happened, Lassiter asks "You see him too, Guster?" in the comic on too is misspelled as "to".
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.