Peach's Bestiary

Peach's Bestiary is an alleged unused mechanic in Super Mario 64. It was said to allow the player to collect various pages in order to fill up a bestiary as another collectable outside of Power Stars. Despite it being allegedly unused, players have said to have the mechanic in their personalized copies.

Overview
Found in the room for the entrance to The Princess's Secret Slide is a small table containing a book. When the player went over to the book and pressed A, a prompt will pop up that says that there are no pages in the book. Next to the book is a lone Toad, who is said to say the following:

"Oh, Mario! It's terrible! This book, it's the Princess'

''bestiary! It's said to have data of all the foes you'll''

come across, but when Bowser invaded, he tore up

all the pages and scattered them throughout the

paintings!"

"...Y'know, if I recall correctly, when I was hiding,

Bowser said to his minions to keep guard of the pages!

Mario, I bet if you were to take out some enemies, you

''could find the missing pages! Hopefully, you can find them''

all, I bet it'll help you a lot on your journey!"

Afterwords, the text box fades away as the game continues. Every enemy is said to have a 25% chance to drop a page of the bestiary, containing a description of said enemy. After collecting a page, a sparkling sound will play, meaning that it has been added to the bestiary. After collecting at least one page, the bestiary can finally be opened, revealing all the pages the player found, which can now be read. By pressing either left or right, the player can turn the page left or right to read more pages, and by pressing B, the player will exit out of the bestiary. Each page has the name and a photo of the enemy, alongside a small description of them and the courses in which they appear, not including shorter, 'bonus' courses (i.e Tower of the Wing Cap) or Bowser courses.

Pages
According to players who have allegedly found pages, no one has found every single page, so it is unknown what exactly happens once a player were to complete the bestiary. This is a list of every single page found by a player so far, as well as their descriptions and locations. Note that some of these descriptions are nothing more than faint recollections, so it's best to take these with a grain of salt.

Speculation
Considering about how nearly-finished looking Peach's Bestiary is, it is speculated that the bestiary was cute quite late into development. Due to enemy's native locations being different from the course they actually appear in, it's theorized that the bestiary was made in a build which, while having the same courses in the original retail release of the game, had different enemy placements.

Despite how nearly-finished it was, the bestiary was cut for unknown reasons, though many theories have sprouted attempting to explain why. The most commonly agreed upon theory is that each enemy in the game was either based on existing enemies that most Mario fans would be familiar with, and/or the enemies were so simple and easy to understand that having a bestiary to describe how they work was considered pointless.

Trivia

 * Peach's Bestiary and the Tattle mechanic from the Paper Mario series are quite similar in a number of ways. It's possible that this cut mechanic could've influenced the Tattle mechanic
 * Interestingly, Enemy's native locations include areas they do not appear in. This could suggest that at one point during development, these enemies could've appeared in these stages, but were cut for one reason or another.