"Petscop is the internet's most popular haunted video game, and no-one knows yet what it all means, nor what it's all leading to."

EG:

Last March, a Youtube channel titled Petscop began releasing Let's Play-style videos of what appeared to be a bargain-bin Playstation One game designed to entice undiscerning children. The video's narrator Paul claims to have just found the Petscop game with cursed cheat-code and spooky note intact.

...

He is a believable streamer, complete with long sections of episodes where he runs around finding very little. These sequences not only build tension, but lend authenticity to proceedings. Like the finest of creepypasta (a digital urban legend spread by reaction, and subject to all the sensationalist tropes therein) Petscop is a cannilly designed found artefact. Even its loading screens are steeped in lore - users who took the time to brighten them revealed strange new images previously indiscernible.

As soon as Paul plays through the aforementioned cheat code, things take a decidedly darker turn. The character descends into a world of black skies and dense grass, and the jangly music of the previous level is replaced with silence. After a long stretch of lonely running, he finds a door. It does not open, and the first episode ends.

Related: A review of Subserial Network:

Subserial Network is one of those games that presents itself as a desktop application, paying homage to old multimedia experiments like the excellent 1996 CD-ROM classic Spycraft: The Great Game and of course to Christine Love's seminal 2010 piece Digital: A Love Story with which it shares a number of visual and narrative themes.

Park describes the game as a 'multi-window experience' but that significantly understates the radical nature of the design. We have lately seen a number of 'computer within a computer' classics, from Digital and Beglitched to Cibele and Her Story, but unlike those games, Subserial Network consists of various programs and files that live on your actual computer desktop, and the wallpaper in these images is just a suggested wallpaper image that they provide in the folder, that I applied to my own Mac desktop. In a way that goes beyond other experiments like Ivan Zanotti's horror game IMSCARED or Robert Yang's Hurt Me Plenty, it breaks that most inviolable of fourth walls, the boundary between the game and the rest of your computer. Games are fiction (which is supposed to stay in-world and in-character) but they are also software (which is supposed to stay obediently in its sandbox).

Thematically that is a perfect metaphor for the story the game tells, which is about characters who are driven to cross forbidden digital thresholds in pursuit of recognition and happiness.