Here is a useful guide regarding this topic, including what the game is, where to find it, and how to stay safe.

Five Nights at Diddy's is a fan-made game that draws heavy inspiration from the FNAF series. Developed by a passionate individual or team (specific credits may vary), the game thrusts players into a nightmarish scenario where they must survive against hostile animatronic characters. The game is set in a fictional restaurant or similar establishment, where these animatronics, designed for entertainment, become deadly when the lights go out.