The Cat officially debuted in Version 1.1 of Chapter 1. The player can pet it, if they find it.
Overview
The Cat was teased a character in the later update of Chapter 1. In early versions of the game, the cat was not used, but the game files could be re-created to make the cat interactive.
Gallery
The cat in-game as of version 1.1.
Ditto, being petted.
Ditto, but still.
The cat's model.
The cat being pet in-game.
The Cat Sneak Peak.