When Lassiter lets Henry out of the car, the car window is open as Lassiter says. The shot cuts away then back to the car and the window is now closed. A minute later, the window is open again.
When the camera pans down after the characters were on the terrace, it's easy to see that there is no access to the terrace from the house.
At the end, when Henry Spencer is seen reading the newspaper article on Shawn and Gus' recent case, the article has two columns around their picture, which read the exact same paragraph. The same paragraph is also repeated beneath the picture. Gus is referred to in the article as "Burtig Gustor."
When Detective Lassiter is showing Henry Spencer his "Crap List", he mentions that Shawn is on it, and when looking closely you can see that he is, but his name is spelled "Sean Spencer." Hillary Clinton is also shown on the list, twice.
Shawn refers to the Battlestar Galactica (1978) helmet as "Captain Adama's." In the original series, *Colonel* Adama was the father of Captain *Apollo*. The term "Captain Adama" wasn't used for the Apollo character until the re-imagined version (Battlestar Galactica (2003)). If Dennis was as hard-core a sci-fi geek as implied, he would never have let Shawn's comment go uncorrected.