The Puppeteer is a human character who appears in FNAC 3 cutscenes. In-game, he is represented by Monster Vinnie. He is heavily implied to be the one possessing Vinnie from the first two games.
Not much is known about the Puppeteer, except that he is an employee and performer at the Rat and Cat Theater.
The Puppeteer only appears in the minigames, otherwise being represented by Monster Vinnie. In the Real Ending, he is first seen scolding the actor in the Rat costume for being drunk on the job. Rat refuses to leave, saying "the show must go on" and resulting in a small fight, which in turn ends with Rat being killed. Though this death was an accident, the next death occurred when Cat came in and saw Rat dead. Cat threatens to call the police, and the Puppeteer kills Cat to ensure his death goes unnoticed--or so he believes. Mary Schmidt has been watching and listening the whole time, unseen and unheard by the employees while hiding. Puppeteer then proceeds to tell a false story to the police, put away his entertaining diploma, and leaves the building, leaving Mary alone. This turns out to be what traumatized Mary so, leading to the events of the game. After Mary gets over she eventually reveals the events and the puppeteer was arrested for his crimes.