A book in the Sleepy Subcon Time Rift features a book called "Proof of Ethical Consumption Under Capitalism", but the pages are all blank.
Express Owls were originally scientists. While most references to this have been removed in the final, their old design can be seen in the portraits in Subcon Forest, and one Mafia makes mention of a "confusing science owl".
Within the game's files there's an unused 2D model for a character named Moon Jumper. What role he would have had isn't exactly known but it is speculated that he, with Queen Vanessa and the Snatcher would compete for the ownership of the Subcon Forest. It's also speculated that Moon Jumper could have been Queen Vanessa's prince, whom she writes about in her diary.
Subcon Well was originally known as Subcon Caves in the beta version and this is still reflected in the game's original soundtrack.
A Moon Penguin voiced Jon Jafari was said to be found in Mafia Town but none are present in the final version. All Moon Penguins in the final are voiced by Marin M. Miller, with Jafari voicing the receptionist at Dead Bird Studio.