Lt. Disher was originally supposed to wear Superman pajamas, but because of licensing wore Capt. America pajamas instead.
You can see on the red book that Monk is reading that it's written by Hy Conrad, one of the producers in the show.
The train station that Mr. Monk goes is the Los Angeles Union Station, which opened in 1939. The exterior shot is the original front, which faces Alameda Street, as opposed to the new entrance at the opposite end on Vignes Street. The interior is the main lobby, which is still in use in 2021.
While in the train station and the man is 'dead' and Monk is jabbing him with a broomstick, he claims "He's acting, let's go, Hume Cronyn". Hume Cronyn was a stage and screen actor. Along with his wife, actress Jessica Tandy they acted in some of the most acclaimed stage shows, movies, and TV.
Mr. Monk asks Dr. Kroger whether anyone ever dies from insomnia. There is a disease called fatal familial insomnia, but insomnia is a symptom; the cause is a type of prion (other types of prions cause Creutzfeldt-Jakob disease, Mad Cow disease, and probably Chronic Wasting Disease in deer). Obviously, lack of sleep can also increase the risk of fatal accidents.