Two of the character names (the hotel manager "Scott Mudgett" and the maintenance man "Eddie Holmes") may be a reference to H. H. Holmes (real name: Herman Webster Mudgett), the infamous 19th Century serial killer associated with the 1893 Chicago World's Fair. The hotel in this episode also shares the name of the Chicago neighborhood (Englewood) where Holmes "Murder Castle" was located.
The epigram to this episode - "Sleep is good, death is better; but of course, the best thing would be to have never been born at all" - is from the German poet Heinrich Heine (1797-1856).
Late in the episode, Monroe quotes the line "Life is a nightmare that prevents one from sleeping," which is from Oscar Wilde.
The images of the Alpen in Monroe's book, bear a strong resemblance to Henry Fuseli's 1781 painting, The Nightmare, which shows a hideous incubus sat on the chest of a sleeping woman and became a popular Romantic / Horror trope. The Alpe is a waking nightmare for its victims.
The episode refers to the Pleiades as a constellation several times but the Pleiades is actually a star cluster in the constellation of Taurus.