Continuity mistake: In the opening scene when young Gus and Shawn are eating ice cream, the amount of ice cream keeps changing throughout the whole scene.
Meat Is Murder, But Murder Is Also Murder - S2-E6
Continuity mistake: The people in the background change in the overhead shot at the end of the episode when Gus walks away from Shawn. (00:41:55)
Meat Is Murder, But Murder Is Also Murder - S2-E6
Continuity mistake: Gus' uncle rips the postcard in half, the shot changes and he rips it in half again.
Psy vs. Psy - S2-E3
Continuity mistake: Shawn and Gus are in front of the Psych office talking about how the other psychic beat Shawn. There are two guys standing in the background, then in one shot there is only one, the next shot there are two again.
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.