When Shawn kicks the carry on luggage, it lands handle down, then after a cut it's handle up, then back to handle down.
When Shawn is outside the Psych office talking to Gus about how the other psychic is bothering him, there are two guys standing in the background leaning against the rail. In the next shot, there is only one guy, then it switches back to two guys in the very next shot.
At the beginning Special Agent Ewing comments that they must have missed the suspect by a few minutes. However, at the end during the flashback, this changes to five minutes.
Counterfeit investigations are done by the Secret Service.
"Special Agent" is used exclusively for FBI agents, not any other branch.
During the final reveal scene at the airport, all the surrounding planes have Canadian registration numbers. As the show is filmed in Canada but takes place in California, an obvious oversight.
While in the "Home Depot" there is a McKenzie Seed company display behind the actors. McKenzie Seed is a Canadian company and wouldn't be sold in Santa Barbara, California.
When Lasseter is commenting on Mildred, he states that it must be an anagram. The proper term is acronym. An anagram is when you mix up the letters of a word to make another word, and an acronym is a group of letters that each stand for a different word.
Shawn claims that 700 hours is almost 20 days but it is almost 30 days.