After speaking to the waitress (Sandra Luesse) in the diner, Jack (Steve Zahn) tells Monk (Tony Shalhoub) he was speaking Guarni, the official language of Paraguay. It is actually one of two official languages of Paraguay, the other being Spanish.
Steve Zahn, appearing as Adrian's brother, Jack, also starred in Joy Ride (2001) as Fuller. Ted Levine, who plays Leland Stottlemeyer in this series, provided the voice (uncredited) for Rusty Nail in the same film.
In Mr. Monk Gets Hypnotized (2008) (2009), a childlike Adrian discovers the joy of the breakfast pancakes his mother never made for him. Here he's working on his own adult OCD version, with obvious teething troubles regarding the irregularity of shapes that happen when cooking with batter.