The pillowcases Monk takes with him are white, but in "Mr. Monk Goes to the Asylum (2002)," Sharona says that he sleeps only on dark-colored pillowcases.
At the pool party, a young man is holding a plastic bottle of Sierra Springs water. The white cap is sealed, then, without being turned, the cap appears unsealed.
The Mexican inspector tells Monk that the victim "won" a free skydiving lesson. But if that is the case, then he would not have been jumping solo on his very first jump.
At the airport, supposedly in Mexico, Monk talks with the pilot of the airplane that carried the skydiver. The tail number of the plane, N8356S, indicates U. S. registry (the "N"). In fact, it's (still?) registered to someone in Simi Valley.
When Sharona finds the dead guy's prescription, she says "Hydroxyzine. That means he was allergic to chlorine." Hydroxyzine is an antihistamine that's prescribed for various allergies as well as for anxiety. It doesn't suggest an allergy to chlorine specifically.
The San Marcos coroner tells Monk that Chip's blood was "hypertonic." Hypertonicity in fluids refers, more or less, to an imbalance in cellular pressure gradients internal and external to the cell. The term the coroner was probably meant to use was "hypervolemic," which refers to excess water/fluid in the blood.
At the opening, with Monk and Sharona at the mailbox, Capt. Stottlemeyer approaches and tells of a problem in "San Macros," mispronouncing the name (San Marcos). Oddly, at the very end, the tag scene, Monk opens a letter from the police there, and he also says "San Macros." Response: Everyone, including the residents of the city, refers to it as San Macros. It is a fictional city.
Near the beginning, when Monk is mailing a letter, the collection box has a hasp and padlock. No American mailbox has a padlock because the lock is built into it.
At the end of the episode, Capt. Alameda says that Dr. Madero is responsible for 3 murders, but it's really 4 - the person he killed in San Francisco, the one mauled by a lion, the one who drowned in midair, and the man he mistakenly hit with his car.
Contrary to what Monk and all the police officers and the coroner seem to believe, it is in fact possible to drown on dry land. However, this can only happen when someone has nearly drowned in water and there is residual water still in their lungs. While it is concluded that Chip couldn't have gone in the motel pool, no one ever tries to determine if he might have gone swimming somewhere else.
When TJ is talking to Sharona at the hotel, he pronounces "expressions" as "espressions."