Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Roblox
The weird noises the Medusa Head gear makes. Just try it out in Catalog Heaven!
This game that is based off a ROBLOX creepypasta named Melvin.
Sometime in July 2014 the popular games were hacked by God knows who, the point is the kids who played those games were probably scared by some of the stuff on there, such as when joining a game you'd be welcomed by an ear piercingly loud alarm noise, or like another case when you joined a game, the entire place was turned incredibly dark and the music that was orignally in the game was changed into what felt like a distorted version(Feels like a Creepypasta.). Not all of it was scary, though.
A good example of the hacks to use would be Person299's Minigames, in which when you die the game shuts down automatically.