Revealing mistake: Whenever you see Shawn and Gus outside it appears to be warm but if you look in the background people are wearing jackets and heavy coats, revealing that during filming it was winter and cold out.
Continuity mistake: When Shawn kicks over the carry-on bag at the end, it lands with the handle on top. The subsequent wide shot shows the bag with the handle on the bottom. The handle is back on top just before the bag is opened.
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.